SGC HF SSB Users Guide

Pierre B. Goral, President

HF-SSB COMMUNICATIONS:

THE POWER TO LOCK IN THE WORLD.

Globally, HF-SSB has literally changed the world. For a minimal investment, it has allowed millions of people - often in amazingly remote settings, often in emergency conditions - to reliably bounce clear voice and data signals across a state, across a continent, over an ocean, or around the world. Without satellites, relay stations, cellular nets, stadium sized antennas or huge user fees. Just some fine equipment, a smart operator and nature's own ionosphere make this possible.

For nearly 25 years, the perfection of HF SSB has been the focus and the life of our company. Our efforts have not gone unnoticed. Today, SGC is a prominent choice of leading corporations, governments, relief agencies, paramilitary

organizations, mariners, aviators, explorers, and scientists - all over the world. They trust our engineering and they value our experience.

A vital part of our company's strategy centers around new product development, with an emphasis on providing quality equipment which remains rugged, reliable and competitively priced. We are focused on providing customer service of the highest standard. Our commitment is to product training and comprehensive after sales

support. Today, SGC is recognized as a world class designer and manufacturer of HF SSB communications products.

At SGC we build communications power tools. Next generation HF-SSB radios, antennas, amplifiers and coupler systems that squeeze more range and clarity out of every watt of HF SSB communications power, are the technology and innovations that have helped SGC emerge as a cutting edge player in the expanding world of HF-SSB.

Actually, SGC was the first company to perfect and mass produce solid-state HF SSB radios, more than 20 years ago.

Today, our focus is an ever higher level of HF SSB refinement and performance. All focused on creating HF SSB voice and data communications systems that are so user friendly

and so powerful, they allow every SGC user to easily lock in the world. SGC - HF SSB Power Tools!

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CONTENTS

CHAPTER 1
USERS OF LONG-RANGE RADIO EQUIPMENT
HF SSB HIGH FREQUENCY SINGLE SIDEBAND...................................................................	7
WHAT IS SSB? ......................................................................................................................................................................	8
SSB'S HIGH EFFICIENCY ...................................................................................................................................................	9
HF SIGNAL CHARACTERISTICS ....................................................................................................................................	10
PROPAGATION ..................................................................................................................................................................	12
NATURAL CYCLES THAT AFFECT PROPAGATION ..................................................................................................	12
HF INTERFERENCE ...........................................................................................................................................................	14
SIGNAL PATHS ..................................................................................................................................................................	15
OPERATING NECESSITIES ..............................................................................................................................................	16
INFORMATION SOURCES................................................................................................................................................	17
OPERATING MODES .........................................................................................................................................................	19
MORSE CODE .....................................................................................................................................................................	19
CW (CONTINUOUS WAVE) .............................................................................................................................................	19
VOICE ..................................................................................................................................................................................	19
AM (AMPLITUDE MODULATION) .................................................................................................................................	19
SSB (SINGLE SIDEBAND) ................................................................................................................................................	20
DATA ...................................................................................................................................................................................	20
VIDEO ..................................................................................................................................................................................	21
HF SSB vs. VHF/UHF RADIO COMMUNICATION SYSTEMS .....................................................................................	22
VHF/UHF COMMUNICATIONS .......................................................................................................................................	22
COVERAGE.........................................................................................................................................................................	23
REPEATERS REQUIRED ON VHF/UHF ..........................................................................................................................	24
NO REPEATERS WITH HF SSB........................................................................................................................................	25
SECURITY ...........................................................................................................................................................................	25
POWER.................................................................................................................................................................................	26
INSTALLATION .................................................................................................................................................................	26
COST ....................................................................................................................................................................................	27
CHAPTER 2
HF TRANSCEIVER SPECIFICATIONS AND FEATURES................................................	29
HF TRANSCEIVER SPECIFICATIONS AND FEATURES .............................................................................................	30
MODES.................................................................................................................................................................................	30
TRANSMITTER/RECEIVER BANDS AND FREQUENCY RANGE ..............................................................................	30
POWER OUTPUT................................................................................................................................................................	30
FREQUENCY STABILITY AND CRYSTAL OVEN ........................................................................................................	31

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FREQUENCY STEP ............................................................................................................................................................	31
SENSITIVITY ......................................................................................................................................................................	31
SELECTIVITY .....................................................................................................................................................................	32
OPERATING TEMPERATURE RANGE ...........................................................................................................................	32
POWER REQUIREMENTS.................................................................................................................................................	32
CURRENT DRAW...............................................................................................................................................................	32
DUTY CYCLE .....................................................................................................................................................................	33
DISPLAY AND ILLUMINATION......................................................................................................................................	33
METERING ..........................................................................................................................................................................	33
MEMORIES .........................................................................................................................................................................	34
SCAN ....................................................................................................................................................................................	34
ALARM ................................................................................................................................................................................	34
AUTO ALARM ....................................................................................................................................................................	34
BREAK-IN KEYING (QSK) ...............................................................................................................................................	34
SIDETONE ...........................................................................................................................................................................	35
FILTERS...............................................................................................................................................................................	35
DSP (DIGITAL SIGNAL PROCESSING) ..........................................................................................................................	35
DSP IN HF COMMUNICATIONS......................................................................................................................................	36
DSP TECHNOLOGY ...........................................................................................................................................................	36
SPEAKER/HEADPHONE/RECORD OUTPUTS ...............................................................................................................	37
AUDIO I/O/ PORTS.............................................................................................................................................................	38
AGC (AUTOMATIC GAIN CONTROL)............................................................................................................................	38
NOISE BLANKER ...............................................................................................................................................................	38
FREQUENCY OFFSETS .....................................................................................................................................................	38
PTT (PUSH-TO-TALK TRANSMITTER) ..........................................................................................................................	38
VOX (VOICE ACTIVATED TRANSMITTER) .................................................................................................................	39
SPEECH PROCESSING ......................................................................................................................................................	39
ATTENUATOR....................................................................................................................................................................	39
SIMPLEX/DUPLEX OPERATION .....................................................................................................................................	39
SQUELCH ............................................................................................................................................................................	39
SPLIT-FREQUENCY OPERATION ...................................................................................................................................	40
SELECTABLE SIDEBANDS ..............................................................................................................................................	40
DATA TRANSMISSION .....................................................................................................................................................	40
COMPUTER CONTROL .....................................................................................................................................................	40
REMOTE CONTROL ..........................................................................................................................................................	41
ALE (AUTOMATIC LINK ESTABLISHMENT)...............................................................................................................	41
ENCRYPTIONS AND SCRAMBLING ..............................................................................................................................	41
GENERAL-COVERAGE RECEIVE ...................................................................................................................................	41
CHANNEL OPERATION....................................................................................................................................................	42
POWER SUPPLIES..............................................................................................................................................................	42
CABLING.............................................................................................................................................................................	42
AC (MAINS) POWER SUPPLIES ......................................................................................................................................	44
TRANSFORMER-RECTIFIER POWER SUPPLIES .........................................................................................................	44
MOBILE POWER SUPPLIES .............................................................................................................................................	45

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SOLAR-POWERED CHARGERS ......................................................................................................................................	46
HUMAN POWERED CHARGERS.....................................................................................................................................	46
CHAPTER 3
HF ANTENNAS, FEEDLINES AND GROUNDS .........................................................................	47
HF ANTENNAS, FEEDLINES & GROUNDS ...................................................................................................................	48
OPERATING ENVIRONMENT..........................................................................................................................................	48
BASE ....................................................................................................................................................................................	48
MOBILE ...............................................................................................................................................................................	48
MARINE...............................................................................................................................................................................	49
FIELD ...................................................................................................................................................................................	49
AERONAUTICAL ...............................................................................................................................................................	50
ANTENNA PATTERN BASICS .........................................................................................................................................	50
ANTENNA CONSTRUCTION BASICS ............................................................................................................................	53
ANTENNA TYPES ..............................................................................................................................................................	54
LONGWIRES AND RANDOM-LENGTH WIRES............................................................................................................	54
VEES AND RHOMBICS .....................................................................................................................................................	55
THE QUARTER WAVE VERTICAL .................................................................................................................................	56
THE VERTICAL WHIP.......................................................................................................................................................	57
THE WINDOM ANTENNA ................................................................................................................................................	57
THE DIPOLE AND ITS VARIATIONS..............................................................................................................................	57
BEAM AND YAGI ANTENNAS........................................................................................................................................	58
LOG-PERIODIC ANTENNA .............................................................................................................................................	58
LOOP ANTENNA................................................................................................................................................................	59
BOXES AND DELTAS .......................................................................................................................................................	59
QUADS.................................................................................................................................................................................	60
MOBILE ANTENNA VARIATIONS .................................................................................................................................	60
FEEDLINES .........................................................................................................................................................................	61
GROUNDING SYSTEMS ...................................................................................................................................................	64
EQUIPMENT GROUNDS ...................................................................................................................................................	64
RF COUNTERPOISES AND GROUND PLANES.............................................................................................................	64
BASE STATION GROUNDS ..............................................................................................................................................	65
FIELD-OPERATION GROUNDS .......................................................................................................................................	66
MOBILE GROUNDS ...........................................................................................................................................................	67
SAILBOAT AND POWERBOAT GROUNDS ...................................................................................................................	68
AIRCRAFT GROUNDS ......................................................................................................................................................	70
GROUND DAMAGE, AGEING AND MAINTENANCE..................................................................................................	70
CHAPTER 4
INSTALLATION ....................................................................................................................................................	71
INSTALLATION .................................................................................................................................................................	72
TRANSCEIVER ...................................................................................................................................................................	72
RUNNING POWER CABLES.............................................................................................................................................	73
CONNECTING AND CONNECTOR TYPES ....................................................................................................................	74

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CONNECTING THE GROUND..........................................................................................................................................	74
CONNECTING THE FEEDLINE........................................................................................................................................	74
CONNECTING THE AUDIO I/O JACK ASSEMBLY ......................................................................................................	74
CONNECTING THE REMOTE CONTROL ......................................................................................................................	75
COUPLER ............................................................................................................................................................................	76
LOCATION ..........................................................................................................................................................................	76
CONNECTION TO POWER ...............................................................................................................................................	76
CONNECTION TO RF GROUND ......................................................................................................................................	77
CONNECTION TO TRANSCEIVER..................................................................................................................................	78
CONNECTION TO ANTENNA ..........................................................................................................................................	78
THE COUPLER IN A HARSH ENVIRONMENT..............................................................................................................	79
ANTENNA ...........................................................................................................................................................................	79
LOCATION ..........................................................................................................................................................................	80
FEEDLINES .........................................................................................................................................................................	81
FEEDTHROUGH CONNECTORS OR HOLES .................................................................................................................	81
FEEDLINE ROUTING ........................................................................................................................................................	81
HARSH ENVIRONMENTS ................................................................................................................................................	82
NOISE AND INTERFERENCE...........................................................................................................................................	82
NATURAL INTERFERENCE .............................................................................................................................................	82
MAN-MADE INTERFERENCE..........................................................................................................................................	83
NOISE REMEDIES AT THE TRANSCEIVER ..................................................................................................................	84
DIGITAL SIGNAL PROCESSING (DSP) ..........................................................................................................................	84
NOISE BLANKER ...............................................................................................................................................................	84
MAGNETIC ANTENNAS ..................................................................................................................................................	84
CHANGE OF FREQUENCY...............................................................................................................................................	85
NOISE REMEDIES AT THE NOISE SOURCE .................................................................................................................	85
ISOLATION AND BY-PASSING .......................................................................................................................................	85
BONDING ............................................................................................................................................................................	86
STATIC COLLECTORS......................................................................................................................................................	86
SHIELDING .........................................................................................................................................................................	87
GROUNDING ......................................................................................................................................................................	87
MOVING THE ANTENNA .................................................................................................................................................	87
POWER CONCEPTS ...........................................................................................................................................................	88
FORWARD POWER............................................................................................................................................................	88
REFLECTED POWER ........................................................................................................................................................	89
STANDING WAVES ...........................................................................................................................................................	89
VSWR ...................................................................................................................................................................................	89
FIELD STRENGTH .............................................................................................................................................................	89
FREQUENCY.......................................................................................................................................................................	90
GAINS AND LEVELS.........................................................................................................................................................	90
DO-IT-YOURSELF LIGHT-BULB DUMMY LOAD........................................................................................................	90
RADIO TEST PROCEDURE...............................................................................................................................................	92
COUPLER TEST PROCEDURE .........................................................................................................................................	93
INSTRUMENTS...................................................................................................................................................................	93
WATTMETER .....................................................................................................................................................................	93
SWR METER .......................................................................................................................................................................	93
FIELD STRENGTH METER...............................................................................................................................................	94

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FREQUENCY COUNTER...................................................................................................................................................	94
IMPEDANCE BRIDGE .......................................................................................................................................................	94
S-METER .............................................................................................................................................................................	94
CHAPTER 5
AMATEUR RADIO..............................................................................................................................................	95
AMATEUR RADIO .............................................................................................................................................................	96
AMATEUR OPERATIONS .................................................................................................................................................	97
COMMERCIAL LICENSING .............................................................................................................................................	98
STATION LICENSES..........................................................................................................................................................	99
OPERATOR LICENSES......................................................................................................................................................	99
CHAPTER 6
MARINE OPERATIONS ...............................................................................................................................	101
MARINE OPERATIONS ...................................................................................................................................................	102
SHIP-TO-SHORE CALLS .................................................................................................................................................	102
TELEPHONE CALLS........................................................................................................................................................	103
SHIP-TO-SHIP CALLS......................................................................................................................................................	105
EMERGENCY CALLS ......................................................................................................................................................	105
CHAPTER 7
SGC'S VISION OF SMART PRODUCTS ........................................................................................	107
THE HISTORY OF SGC....................................................................................................................................................	108
SGC PRODUCT LINE .......................................................................................................................................................	109
THE SGC VISION OF HF .................................................................................................................................................	109
MARKETING PLANS .......................................................................................................................................................	110
THE EXPORT PICTURE...................................................................................................................................................	111
THE SG-2000 HF TRANSCEIVER...................................................................................................................................	112
THE SG-2000: A NEW STYLE OF OPERATION ...........................................................................................................	115
SGC SG-2000 POWERTALKTM........................................................................................................................................	116
ADSPTM NOISE REDUCTION .........................................................................................................................................	117
SNSTM NOISE REDUCTION ............................................................................................................................................	118
FIRST MOBILE DSP TRANSCEIVER ............................................................................................................................	118
VISUAL DSP FILTER DISPLAY .....................................................................................................................................	118
PROGRAMMABLE DIGITAL FILTERS.........................................................................................................................	118
PRE-PROGRAMMED FILTER SETTINGS.....................................................................................................................	119
NOTCH FILTER ................................................................................................................................................................	119
VARIABLE BANDPASS, LOW-PASS, AND HIGH-PASS FILTERS ...........................................................................	119
UPGRADE DSP HEAD .....................................................................................................................................................	119
REMOVABLE HEAD........................................................................................................................................................	119
SIMPLE DESIGN OF FRONT-PANEL CONTROLS ......................................................................................................	120
BIG-POWER/SMALL PACKAGE....................................................................................................................................	120
TESTED FOR HIGH QUALITY .......................................................................................................................................	120
SG-2000 FEATURES AND BENEFITS............................................................................................................................	121

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QMSTM (QUICK MOUNT SYSTEM) ...............................................................................................................................	123
QMS FEATURES AND BENEFITS .................................................................................................................................	127
SG-230 SMARTUNERTM ..................................................................................................................................................	128
SG-230 FEATURES AND BENEFITS..............................................................................................................................	131
SG-303, SG-103 AND SG-104 ANTENNA SYSTEMS ...................................................................................................	133
SG-303 FEATURES AND BENFITS ................................................................................................................................	134
SG-500 SMART POWERCUBETM....................................................................................................................................	135
SG-500 SMART POWERCUBETM BENEFITS & FEATURES.......................................................................................	136
THE OTHER SGC PRODUCTS........................................................................................................................................	136
PRC-2250 MIL ...................................................................................................................................................................	137
SG-715 MANPACK ...........................................................................................................................................................	137
SG-1000-1 LINEAR AMPLIFIER .....................................................................................................................................	138
FEATURES/BENEFITS OF SG-2000 ...............................................................................................................................	139
QMS FEATURES AND BENEFITS .................................................................................................................................	140
SG-230 FEATURES & BENEFITS ...................................................................................................................................	141
SG-303 FEATURES & BENEFITS ...................................................................................................................................	142
CHAPTER 8
GLOSSARY & GENARAL ELECTRONIC AND HF SSB ABBREVIATIONS .143
SGC IDEAS AND OPPORTUNITIES) ............................................................................................................................	148
WARRANTY .....................................................................................................................................................................	149
SGC QUOTATION REQUEST FORM .............................................................................................................................	150

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CHAPTER 1

USERS OF LONG-RANGE

RADIO EQUIPMENT

HF-SSB

HIGH FREQUENCY

SINGLE SIDEBAND

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USERS OF LONG-RANGE RADIO EQUIPMENT

MARINE & FISHING Marine and fishing vessels require HF communications. Transmissions in the HF range can often reach thousands of miles, and when a ship is far from shore, no other communications system would be as effective and inexpensive.

AVIATION Although aircraft are often flying in areas where line-of-sight communications (such as UHF and VHF frequencies) are useful, HF equipment is necessary for any long-distance transmissions.

COMMERCIAL Commercial users of the HF spectrum typically use this equipment to contact personnel in distant or remote areas, where any other medium would be either impossible or too expensive.

MILITARY Various branches of the military have traditionally used the HF bands for base and field

communications.

GOVERNMENT Because not all government communications cover short distances, HF frequencies are used exclusively in sensitive long distance communications and in remote regions which are difficult to reach, such as deserts, dense forests and mountainous regions. And, for embassy transmissions, HF is a must.

LAW ENFORCEMENT Like other government communications, law enforcement can be served with UHF and VHF equipment. However, for long-distance operations, the national branches of U.S. law enforcement, such as the FBI, use HF frequencies.

AMATEUR RADIO Amateur operators (sometimes known as "hams") are licensed hobbyists who communicate via two-way radio on a number of frequency bands. As a result of the frequencies and the powers that they use, amateurs are commonly heard around the world.

WHAT IS SSB?

Before you can understand what SSB is, you must understand how audio is transmitted via radio waves. The method by which audio is impressed on a radio signal is called modulation. The two types of modulation that most people are familiar with are AM (amplitude modulation) and FM (frequency modulation). The AM and FM broadcast bands were so named as a result of these two types of modulation. In an AM-modulated radio signal, a base signal, called the carrier, is continuously broadcast. The two modulating signals are called the sidebands. Any audio that you hear on an AM broadcast station is from the two sidebands. When the radio station is not transmitting any sound, you can still hear that a signal is present; that is the carrier.

These two modulating (audio) sidebands are located on either side of the carrier signal--one just above, the

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other just below. As a result, the sideband located just above the carrier frequency is called the upper sideband and that which is located just below the carrier frequency is called the lower sideband.

The pieces that fit together to form an AM broadcast signal are quite important. Although AM signals were transmitted almost exclusively for decades, it was discovered that the AM signal could be dissected. The first amateur radio operators to experiment with these processes often used both sidebands without the carrier. This is known as double sideband

(DSB). DSB was typically used in the earlier operations because it was much easier to strip out just the carrier than to strip out the carrier and one of the sidebands. Several years later (and still true today), it was much more common in the amateur bands to merely transmit using one of the sidebands, which is known as single sideband (SSB).

Single sideband transmissions can either consist of just the lower sideband (LSB) or the upper sideband (USB).

If you listen to an SSB signal on an AM modulation receiver, the voices are altered and sound a lot like cartoon ducks. As a result, you must have a special SSB receiver to listen to these transmissions. Although this was often difficult for the amateur radio operators of the 1950's, it is no longer a problem with today's modern SSB transceivers, such as the SG-2000.

You might wonder why SSB modulation is used for some applications and AM is used for broadcasting. It is a necessity for broadcasters to have excellent fidelity when transmitting music; otherwise, the typical radio listener will tune to another station. In order to achieve excellent fidelity when transmitting music, both sidebands and the carrier are necessary. To produce this AM signal, the transmitter is, in effect, working as three transmitters: one to produce a strong carrier for each of the sidebands, an upper sideband, and a lower sideband. The result is that approximately half of the transmitter power is "wasted" on a blank carrier and the rest of the power is divided between the two sidebands. As a result, the actual audio output from a 600-watt AM transmitter (300 watts of carrier + 150 watts on each sideband) would be the same as the SG-2000 150-watt SSB transmitter.

SSB'S HIGH EFFICIENCY

Let's run some numbers: Suppose you have a typical 5-kW broadcast transmitter. You will only be able to impress 2.5 kW of audio power on that signal. This means that each of the two sidebands will have only

1.25 kW of power.

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A single-sideband signal removes the carrier and one sideband and concentrates all of it's energy in the remaining sideband.

SSB Power! The actual audio output of a 150-watt SSB transmitter is the same as a 600-watt

AM transmitter.

This is the key to highly effective communications using single sideband. A single sideband signal removes the carrier and one sideband and concentrates all of its energy in one sideband. Thus, a 1-kW SSB signal will "talk" as far as a

4-kW conventional AM or FM transmitter. It is why long distances can be covered effectively with SSB.

Single sideband's benefit is not only evident on transmission. The reverse happens on receive. When you work out the math, the efficiency with an SSB signal is 16 times greater than with a conventional AM signal.

HF SIGNAL CHARACTERISTICS

HF (high frequency) is synonymous with the more familiar term, shortwave. The only difference is that HF is typically used when discussing two-way and point-to-point communications. Shortwave is typically used when referring to broadcast stations in the same range. In amateur radio, both terms are frequently used.

The HF band extends from 1700 to 30,000 kHz (1.7 to 30 MHz). To give some perspective to these numbers,

COASTAL COM-

AMATEUR

=

VHF

TV

BROADCAST LORANMUNICATIONS

HIGH SEAS CHANNELS

= CB

TV 2-6

FM

MARINE

7-13

.5	1.61.82			3	4	6	8	12	16	22 30 56				88	108	156	176
						FREQUENCY (MHZ)
						HF									VHF

the AM broadcast band runs from 540 to 1700 kHz, the Citizen's Band (CB) runs from 26,960 to 27,230 kHz (within the HF band), and television channel 2 is on 54,000 kHz. Each of these sample frequencies has different

		characteristics, and it is vitally important to learn this information so that you can
	The HF high
		effectively use the HF spectrum.
	frequency band
	extends from	When talking about HF, most people list the frequencies in either kHz (kilohertz) or
	1700 to	MHz (megahertz). This is a matter of convenience only. The base rate for frequency is the
	30,000 kHz	hertz (Hz), named after Heinrich Hertz, an important "father of radio." One kHz equals
	(1.7 to 30 MHz).
		1000 Hz and one MHz equals 1,000 kHz.

The Hz divisions of the radio spectrum aren't arbitrarily chosen hashmarks to divide your radio dial into usable little pieces. Instead, the divisions relate directly to the frequency. Signals such as light, radio, and sound are all waves. These waves travel through the air in a manner that is somewhat similar to waves in a pond. Each radio wave has a peak and a valley. The length of each radio wave is (not surprisingly) known as the wavelength. Radio waves

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travel at the speed of light, so the longer each wave is, the fewer waves can arrive in one second. The number of waves that arrive per second determines the frequency. Although the wavelength and the frequency are different ways of saying the same thing, wavelengths for radio are rarely given. In the 1920's through the 1940's, the wavelength was more frequently used than the frequency, however. This was probably the case because the wavelength seemed like a more tangible measurement at the time. The wavelength of the radio signal is also important because it determines the length of the antenna that you will need for receiving and especially for transmitting. Antennas are covered later in this user guide.

Because of the signal characteristics on the AM and FM broadcast bands, combined with the less effective internal antennas, radio signals are often thought of as being used for primarily local reception (100 miles or so). However, with two-way communications in the HF band, you are not listening for entertainment to the strongest station that you can find. You are attempting to communicate with a particular station under what could be lifethreatening circumstances.

In the 1910's and 1920's, it was thought by most radio enthusiasts that the "wavelengths above 180 meters" were useless. In effect, these people believed that the frequencies above the top of today's AM broadcast band were unusable. Little did they know that the opposite was true for communications over medium to long distances. The reason that these pioneers were misled was because they didn't yet understand the methods by which radio waves travel.

These methods are known as propagation, but they can be simplified to provide a basic understanding of the subject. When you listen to a local AM broadcast station, you are receiving the ground wave signal. The ground wave travels along the ground for often a hundred miles or so from the transmitter location. The low frequencies, such as those in the AM broadcast band and lower, produce very large ground-wave patterns. The ground waves are very important because they produce solid, virtually fade-free reception.

The other major method by which radio signals reach your receiver are the sky waves . Sky waves travel toward the sky, rather than hang out on the ground. You would not be able to hear the sky-wave signals, except for the ionosphere. The ionosphere is many miles above the earth, where the air is "thin"containing few molecules. Here, the ionosphere is bombarded by x-rays, ultraviolet rays, and other forms of high-frequency radiation. The energy from the sun ionizes this layer by stripping electrons from the atoms.

"Skywaves" travel immense distances by multiple "bounces" off the ionosphere.

When a sky-wave signal reaches the ionosphere, it will either pass through it or the layer will refract the signal and bend it back to earth. The signal can be heard in the area where the signal reaches the earth, but depending on a number of variables, there might be an area where no signal from that particular transmitter is audible between the ground wave and where the sky wave landed. This area is the skip zone. After the sky-wave signal bounces on the earth, it will return toward the sky again. Again, the signal will be refracted by the ionosphere and return to

the earth.

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Frequency (MUF) is lowest at night and highest during

the day.

The Maximum Usable

The Critical Angle of Radiation is the steepest angle at which a radio signal can be refracted by the ionosphere.

B
A
B
A
0m
100		iles
0	mil
400
		es

DURING THE DAY A 12 MHZ SIGNAL (A) WOULD PROPAGATE OUT TO 1,000 MILES, WHILE AT THE SAME TIME, A 17 MHZ SIGNAL (B) COULD REACH 4,000 MILES OR MORE BECAUSE OF THE INCREASED REFLECTION ANGLE.

If the HF signals all bent and bounced off the ionosphere with no losses in signal strength, HF stations around the world would be heard across the earth with perfect signals (something like if a "super ball" was sent bouncing in a frictionless room). Whenever radio signals are refracted by the ionosphere or bounce from the earth, some of the energy is changed into heat. This is known as absorption. As a result, the signal at the first skip is stronger than the signal at the second skip, and so on. After several skips, typical HF signals will dissipate.

The skip and ground waves can be remarkably close together. It is not unusual for one station to receive a booming signal that nearly pegs the meter of a receiver. At the same time, a nearby station cannot hear a trace of the sending station even though using a better receiver with a better antenna. The first station was receiving either the ground wave or the first skip and the other station was located somewhere between these two.

PROPAGATION

If the HF users only had skip to contend with, the theories and uses of the HF spectrum would be simple. But several other factors also come into play. The critical angle of radiation is the steepest angle at which a radio signal can be refracted by the ionosphere. The critical angle depends on the frequency that is being used, the time of year, the time of day, etc. Sometimes a signal that shoots straight up from the antenna will be refracted by the ionosphere. In this case, the critical angle would be 0 degrees. In another case, the signal

might slice through the ionosphere and continue into space. From this signal, you would not be able to determine the critical angle; you would only know that the sky-wave signal was above the critical angle.

NATURAL CYCLES THAT AFFECT PROPAGATION

Aside from the critical angle, the frequency used can also affect whether the signal will be passed through or refracted by the ionosphere. When a signal penetrates through the ionosphere without being refracted, the signal is said to operate above the Maximum Usable Frequency (MUF)

. The MUF is not a set frequency; it varies greatly, depending on the time of day and the part of the world that you are attempting to contact. Nearly the opposite of the MUF is the lowest usable frequency (LUF). However, the LUF has nothing to do with whether or not

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During years of high sunspot activity, the MUF dramatically

7K

6K

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4K

17 MHZ

3K

2K

12 MHZ

1.5K

1KL

8 MHZ

4 MHZ

0 2 4 6 8 10 12 14 16 18 20 22 24

LOCAL TIME

MAXIMUM RANGE FOR VARIOUS MARINE BANDS AS A FUNCTIO OF TIME OF DAY

the signal will be refracted by the ionosphere; instead, it is the lowest frequency that you can use to reach a particular region (using a base standard amount of power).

In the daylight hours, the MUF is highest and in night hours, it is lower. There is also some seasonality, too. In the winter, with longer hours of darkness, the MUF is generally lower than the summer when the MUF is higher. Likewise, during the hours of darkness, when the ionosphere is less ionized, the LUF is lower, and during the daylight hours, it is much higher. The MUF and the LUF provide the boundaries between which you should operate the transceiver in order to make your contacts.

As mentioned in the previous paragraphs, propagation is affected by cyclical environmental conditions. The shortest of these conditions is the day/night cycle. In general, the transmitting and receiving conditions are by far the best in the nighttime hours. During the daytime, the MUF and LUF both rise and in order to talk across great distances, less reliable (because of the very long skip) higher frequencies must be used.

The next environmental cycle that affects propagation is the season of the year. The winter/summer cycles are somewhat like the day/night cycles, except to a lesser extent. In general, the MUF and LUF will both be higher in the summer and lower in the winter. Also, the noise from thunder storms and other natural phenomena are much higher during the summer. In fact, except for local transmissions, communications in the 1700 to 3000 kHz range during the summertime are of limited regular use.

The longest environmental cycle that affects propagation is the sunspot cycle. Before the age of radio, it was noticed that the number of solar storms (sun spots) varies from year to year. Also, the number of sunspots per year was not entirely random. The number of solar storms during a good propagational month is above 150 and the number during a weak month is often less than 30. After many years of studying these results, it was determined

that the sunspot cycle reaches its peak approximately every 11 years and that these cycles have a great impact on radio propagation. Between these peaks are several years with very low sunspot activity. During years with high sunspot activity, the MUF dramatically increases and long-distance communications across much of the HF band is possible. During the peak of the last sunspot cycle, in 1989, the MUF was often above 30 MHz! When the cycle is at its low point, the MUF decreases and much less of the HF band is usable for long-range communications. Generally, the frequencies above 10000 kHz dramatically improve during the peak years of the sunspot cycle, and the frequencies below 10000 kHz are much less affected.

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Fading is the most common form of propagational interference.

Noise consists of natural (e.g. thunder) and man-made (e.g. fluorescent lighting) interference.

HF INTERFERENCE

Although the long distances that HF radio signals can be received is amazing, in comparison to the other radio bands, several types of distance-related interference can ruin reception or make listening

unpleasant. The most widespread type of interference fits under the broad heading of noise. Noise consists of natural and man-made noise. Natural noise is produced by everything from thunder storms to planets (hence, radio telescopes). Thunder storms are the worst because they cause very loud crashes; because of the long distances that shortwave signals travel, the noise produced by thunderstorms is also likely to travel hundreds of miles (or

further). Even if the weather is clear (you should never operate HF equipment during a local thunderstorm!), a distant thunderstorm could ruin your reception of a weak station that would otherwise be audible at your location.

Man-made interference can arrive from a vast variety of sources. If nothing else, at least most man-made interference is limited in its range; most is limited to the building that the equipment is located in or to a severalblock surrounding area. One of the worst causes of man-made interference is caused by fluorescent lights, which create a medium-strength buzz across the HF range, although it is often at its worst on the lower frequencies. In fact, fluorescent lights near an antenna can drown a normally usable signal. If your radio is located near computers, it will probably receive a light buzz across the bands and much stronger "bleeps." These interference problems are covered further in this user guide.

Adjacent-channel interference is a special type of man-made interference where a station from a nearby frequency is "washing over" or "splattering across" another. A somewhat similar type of interference is co-channel interference, where the interfering station is on the same frequency. A good example of co-channel interference is the 1400 to 1500 kHz "graveyard" region of the AM broadcast band in the evening hours, where dozens of signals are all "fighting" to be heard.

Other types of HF interference cause signal distortion from the propagational effects. One of the most interesting effects is polar echo, which occurs when one component of a radio signal takes an East-West path and another arrives over one of the poles of the Earth. Most every morning, one can tune into one of the BBC broadcast transmitters and hear the effect of polar echo. Because the signals take different paths, they arrive at different times, creating an echo on the audio signal. During the lightest effects, the voices sound a bit "boomy;" at worst, the delay is so long that the programming is difficult to understand. A related phenomena is polar flutter, where the signal

passes over one of the poles and very quickly fades up and down in strength, creating a "fluttery" sound.

Fading is the most common and damaging form of propagational interference. The two most common types of fading are selective fading and multipath fading. With selective

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fading, the ionosphere changes orientation quickly and the reception is altered (somewhat like a ripple passing through the signal). Because of these effects, it is best to use the narrowest mode possible, if selective fading is a problem. As a result, FM and AM signals are especially prone to selective fading, SSB is slightly affected, and the CW mode is almost free from selective fading. The other type, multipath fading, occurs when signals take different paths to arrive at the same location. Multipath fading is a variation of polar echo; instead of the signals creating an echo effect, the phase of the signals are altered as they as refracted by the atmosphere. As a result, the received signal fades in and out.

The last major propagational effect does not actually cause interference to a signal; it absorbs it. Although sun spots are beneficial to propagation as a whole, solar flares destroy communications. During a solar storm, communications across a wide frequency range can suddenly be cut off. Many listeners have thought that their receivers either weren't working or that the exterior antenna had come down because virtually no signals were audible. Instead, they had turned on their radios during a major solar flare. On the other hand, other listeners had thought they were listening during a solar flare, but actually didn't have their antenna connected or they had tuned their radio above the MUF or below the LUF.

SIGNAL PATHS

As covered in the preceding section, signals take various routes to travel to a receiver from the transmitter. The problems that can result from signal paths include polar flutter and echo, and multipath fading.

The signal path is also important when attempting to contact or receive signals from a particular area. When you receive a signal, you can typically assume that it took the shortest path to reach you (i.e. you could connect the points between the transmitting and receiving locations with a line on a globe). This is known as short-path reception. Exceptions to this rule occur when two or more different paths are nearly the same distance (such as the BBC example of polar flutter, where the north-south path isn't much longer than the east-west path).

The other major signal path is the long path. The long-path radio signal travels the opposite direction from the short-path signal. For example, the long-path signal from the BBC transmitter (mentioned earlier) would be east: across Europe, Asia, the Pacific Ocean, most of North America, and finally it would arrive in Pennsylvania. As you can imagine, the signals received via long path are often very weak--especially if the long path was very long and the frequency is low. On the other hand, if the station is on the other side of the world and there is little difference between the long path and the short path, you could be receiving either or both. This case occurred recently to a listener on the east coast of the USA who was listening to a small, private broadcast station from New Zealand - 12 time zones away. At the same time he was listening to it, it was also being heard throughout North America and in Germany. Because the signals were generally a bit better in the West and Midwest, we can assume that he heard the Pacific Ocean-to-Western North America route, rather than the one that passed through Asia and Europe.

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The Grey Line region is the part of Earth that is neither in darkness or daylight-the ionosphere is highly efficient at these times.

One of the most intriguing propagational anomalies is the effect of the grey line on HF radio transmissions. The grey line region is the part of the world that is neither in darkness nor in daylight. Because two grey-line stripes are constantly moving around the earth, the propagational alterations are very brief (usually only about an hour or so in length). Many amateurs and hard core radio listeners actively scour the bands at sunrise or

sunset. The ionosphere is highly efficient at these times, so listeners can often pull in some amazing catches. Grey-line propagation is probably of far less interest to those who use the radio bands in conjunction with their occupation. If you are one of these users, chances are that grey-line propagation will be either a curiosity or a nuisance, as more stations that could cause interference to your signal become audible.

OPERATING NECESSITIES

Because HF communications are capable of covering such large distances and because they are so complex, you must plan out your system and your operating techniques in advance. Of course, in order to participate in two-way communications in the HF bands, you must have a receiver, a transmitter (these two are usually combined to form a transceiver), and an antenna. The type of antenna that you choose, the manner in which you construct it, and the ground system that it connects with are all key factors in the success of your

operations. HF transceivers vary greatly in type, power, construction, frequency ranges, operating modes, features, etc., so you must be sure that you purchase a model that best suits your requirements. SGC transceivers and antennas are covered further in this user guide.

	Depending on your location, the frequencies that you are allocated to use, and the	For privacy, and to
	distance from your contacts, the amount of power output that you will require will vary. In	avoid conflict with
	any case, only use as much power as necessary to make the contact. If you use more power,	other signals, only
	many more people will listen to your transmissions and (especially for amateur radio	use as much power
		as necessary to
	operators) your signal could cause interference in the over-crowded amateur bands. As a
		make the contact.
	result, some transceivers, including some of those from SGC, allow you to continuously
	decrease the power output.

In order to effectively communicate on the HF bands, you will probably need to spend some time "studying" the propagational effects first hand. The best way to do this is to purchase or borrow an inexpensive generalcoverage shortwave receiver or a transceiver, if you don't already own one. Install an antenna and listen across the shortwave bands. The shortwave broadcast stations are fun and interesting to listen to, but most use tremendous transmitter powers--often as great as 500,000 watts output! As a result, you cannot really assess the range of your signal (or someone else's) just by listening to these broadcasters.

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Some of the best amateur radio publications are available from the Amateur Radio

Relay League

Use beacon stations to determine broadcast

The best indications of the bands, the distance of skip, and the distances that you can cover are by listening to stations in the bands (the general frequency areas) that you will be working or by listening to nearby amateur radio

bands. Some beacon stations operate in the amateur radio bands to provide radio enthusiasts with an as-it-happens guide to propagation conditions. Beacon stations usually transmit their call sign over and over in Morse code, according to a particular schedule (often 24 hours per day). If you listen to these beacons, know the power and locations, you can use

them as an accurate yardstick to measure the conditions. If you are an amateur radio operator, you can check into several nets (networks) and ask those involved for an outlook on the present and upcoming propagation conditions.

Listening is one the most important aspects of having successful operations. It might not make a difference if you are using a 30-watt transceiver to communicate with someone a few miles away, but radio experience and good listening skills are a must for long-distance communications. Because of the static, fading, and interference that sometimes plagues the HF frequencies over long distances, you must be able to mentally "filter out" this noise. Experienced "ears" are able to log relatively low-powered AM broadcast outlets while the untrained listener wouldn't hear the broadcaster at all. It will sound like static to them!

INFORMATION SOURCES

In addition to gaining experience by listening to the HF bands, it is very important to keep up to date with various sources of outside information. The outside sources can be either in broadcast or written form. Some of the best amateur radio publications are available from the Amateur Radio Relay League (ARRL). The ARRL sells a number of excellent books of various aspects of the amateur radio hobby, and most of these books relate quite well to other HF radio services. In addition, the ARRL also produces one of the best amateur

radio magazines, QST. For more information on the products and services available from the ARRL, contact: ARRL, 225 Main St., Newington, CT 06111, USA.

Another publisher of technical books is TAB/McGraw-Hill. In addition to selling a number of beginner-, intermediate-, and advanced-level books on electronics, shortwave, and computers, the company also offers one of the best antenna books available. Joe Carr's Practical Antenna Handbook (2nd Edition), covers most every practical antenna design with a down-to-earth approach. For a catalog, write to: TAB/McGraw-Hill, Blue Ridge Summit, PA 17214-0850, USA or call [phone].

Two excellent annual guides to HF/shortwave broadcast listening are available. The World Radio TV Handbook features hundreds of pages of frequency listings, addresses, transmitter sites for AM, HF/shortwave, and television broadcast stations around the world. For more information, write to: WRTH, BPI Communications, 1515

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Broadway, New York, NY 10036, USA. The Passport to World Band Radio covers the same general topic as the WRTH, but it features less raw information and more interpretations of information and trends in international broadcasting. For more information, write to: Passport to World Band Radio, IBS, Box 300, Penn's Park, PA 18943, USA. Whether or not you are interested in HF/shortwave broadcasting, either of these books are invaluable if you need to discover what Latin American stations are fading into the 6200 kHz area marine frequencies or what African broadcasters are booming into the 40-meter amateur band.

Aside from QST, several other informative amateur radio magazines are available. CQ is now in its 50th anniversary and it is available on newsstands or from: CQ, 76 North Broadway, Hicksville, NY 11801, USA. 73 Amateur Radio Today, 70 Route 202 North, Peterborough, NH 03458, USA covers the amateur radio hobby, but seems to go more for the homebrewing/kit-building angle. All three of the major amateur radio magazines cover propagation from month to month, and they feature practical information about how to make the most of the varying HF conditions. Also, they all have interesting tips, modifications, and antenna projects to make your operating easier and more effective.

Several other magazines might be of interest to those who are interested in HF broadcasts or to government, military, or marine operators. Monitoring Times and Popular Communications magazines cover a variety of radiolistening topics and columns, from longwave through microwave communications. For more information, write to: Monitoring Times, 140 Dog Branch Rd, Brasstown, NC 28902, USA [phone] and Popular Communications, 76 North Broadway, Hicksville, NY 11801, USA.

For more up-to-date information on the propagational conditions, you can listen to radio stations WWV and WWVH, which are the two time and frequency standard stations for the United States. Being a time station means both of these stations only broadcast time pips and the tone at the top the minute, along with announcements as such. WWV and WWVH are set to an atomic clock, which ensures that they are exactly on time. Being a frequency standard means that the stations are exactly on frequency, and they can be used to calibrate transceivers or frequency counters. WWV (from Ft. Collins, Colorado) and WWVH (from Kauai, Hawaii) both broadcast on 2500, 5000, 10000, and 15000 kHz. WWV also broadcasts on 20000 kHz. The two broadcasts are exactly the same, except that WWV features a male announcer for the time checks and WWVH airs a female announcer.

Every hour (at 18 minutes past the hour on WWV and 45 minutes past the hour on WWVH), the stations broadcast propagation reports. These reports are updated daily between 2100 and 2200 UTC and they are the most up-to-date information that is available (short of kidnapping an ionospheric scientist).

WWV and WWVH broadcast information about three different propagational factors: the A index, the K index, and the solar flux. The A index and K index are related values that reflect the amount of geomagnetic activity in the ionosphere. This explanation sounds complicated and it is. What is important to know is that the lower the numbers are, the quieter the conditions are; the higher the number are, the more stormy the ionospheric conditions are. If the A and K indexes are very low (0-10 for the A and 0-3 for the K), the propagation should be better. The last of the

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announced WWV/WWVH propagation conditions is the solar flux. The solar flux is directly proportional to the sunspot number, so as covered earlier, the higher solar flux number (which would occur near the peak of the sunspot cycle) makes for much better propagation on the frequencies above 10000 kHz.

OPERATING MODES

Over the HF spectrum, a number of different operating modes are used for two-way communications. The operating mode is a format of the data and the manner in which it is transmitted. For example, although SSB and AM (covered earlier) are both in the voice format, they are transmitted in different manners. The following modes are used frequently across the HF spectrum.

MORSE CODE

CW (Continuous Wave) CW is a binary code that consists of "dits" and "dahs" as a transmitter is being keyed on and off. Although a number of different codes have been used since the days of the telegraph, the only one that is widely used is Morse code. All amateur radio operators who use the HF bands are required to send and receive Morse code at at least five words per minute (wpm). CW might appear to be outmoded now that today's computers can send and receive many types of digital communications reliably. However, the CW signal is very efficient because only the pattern of the signal (not the audio on the signal) needs to be understood and because the signal can be very narrow. As a result, CW is the most reliable form of communications for human operators.

VOICE

AM (Amplitude Modulation) As was covered earlier, the AM mode consists of a base carrier, a modulated upper sideband, and a modulated lower sideband. However, some of the newer transceivers that have this mode use the SSB signal with a carrier inserted to produce a faux AM signal. Although true AM is the favorite mode of AM band and shortwave broadcasters, it is rarely used elsewhere because it is inefficient and because it requires a large amount of space in the already-crowded amateur bands. For the most part, the only AM two-way stations currently on the air are nostalgic amateurs who love the broadcast-quality audio from this mode.

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SSB (SINGLE SIDEBAND)

As was covered earlier, SSB is one half of the voice component of the standard AM signal. The SSB mode is nearly always used for two-way communications across the HF spectrum. SSB is so popular because the mode is much more efficient than any other voice mode and because the signals are narrower, so it is rarely hampered by fading.

DATA

RTTY (Radio Teletype) RTTY (often pronounced as "ritty") is one of the earliest forms of data communications. In this system, printed data is transmitted via a high-speed machine, rather than hand-keyed, as is the case with CW communications. Although CW is a form of data communications, it is copied by a human operator. Nobody can copy RTTY by ear. RTTY is a completely different world of communications from the voice modes. To try to thoroughly cover this topic here would be somewhat like trying to cover every aspect of DOS and Windows in one introductory book on computers. As a result, the information in the following paragraphs is only intended to provide some basic information and to whet your interest in this branch of the technology.

In order to send and receive RTTY, you must have other equipment in addition to the standard HF transceiver/antenna combination. Today, the most common arrangement would be to interface a personal computer with your transceiver and purchase the appropriate demodulating/modulating software or a computer interface.

If no computer is available, then you are stuck with purchasing a modulator/demodulator (modem), a monitor, and a printer.

The three major branches of RTTY communications are Baudot, AMTOR, and ASCII. The characters in Baudot code are formed by blocks of five-digit binary codes and an initial arrow. There are "old-timer"amateur radio/MARS friends who who have Baudot RTTY units from the mid-century. These hulking blocks of steel are true mechanical wonders--something like a giant typewriter and printer combination in a desk-sized case full of gears. The catch with Baudot code is that it directly intermeshes with these mechanical printers and it is prone to interference--fades, static, and man-made interference, which cause errors in the received messages.

AMTOR is (simplified) RTTY Baudot code that has been modified to add various error-detection and correction enhancements. The AMTOR system corrects data by sending it in time-delayed chunks. The transceivers are connected to a "smart box"--a computer modulator/demodulator. Then, the transmitting station will send a block of data and the receiving station will receive it and transmit a signal back to verify that it received the signal. If the signals from the transmitting station are not received properly, then the receiving station will transmit a signal for the other station to repeat that block of text. This process will continue until the entire message is sent. Technically,

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this transmit/receive/verify process is called handshaking.

SITOR is a version of AMTOR that is used especially for marine and weather information. As a result, SITOR is mostly important for marine operators. Some Coast Guard and Marine Coast stations operate in the commercial marine bands. Otherwise, some press frequencies in the 8 and 12 MHz bands are still audible. Just below the AM broadcast band on 518 kHz is a good bet for hearing U.S. Coast Guard information, which is broadcast to ships at sea.

ASCII is a very familiar term to many people in the 1990's because of the popularity of computers. Nearly every computer editing system uses ASCII or some derivative of ASCII. As a result, it makes sense that ASCII would also be used to communicate data on the HF bands. Like Morse code and Baudot code, ASCII is a binary code. However, it differs from Morse because it uses 0 and 1 in the code (instead of dots and dashes) and it differs from Baudot code because it uses a seven-digit instead of a five-digit code.

When speaking of digital transmissions, whether RTTY radio transmissions, or computer/modem transmissions, the baud rate is the speed by which the information is transferred. The baud rate is determined by the bits of information (each electrical impulse) that flow through the system. Typical baud rates for computers are 300, 1200, 2400, 9600, 14,400, and 28,800 bps (bits per second). By the mid 1990's, most of the transmissions were in the last three speeds. The baud rates for RTTY are generally much slower because of the lower quality for the transmissions (static crashes, fades, adjacent-channel interference, etc.). Most RTTY baud rates are 100 bps or less.

One of the most interesting forms of data communications is packet radio. Packet radio is so named because information is broken up into small packets and sent hither through the radio waves. Unlike the typical forms of data communications (where the send and receive process is very noticeable), packet radio is more like having a wireless computer BBS. The packet messages can be stored and recalled at a later date, the communications are relatively error-free, and the information can be sent to many interconnected stations.

The data transmissions are interesting and useful because they can be used essentially like E-Mail. RTTY doesn't have the advantages that it once had, now that the Internet has become "the information highway." Still, RTTY and packet radio are free to use if you are licensed to do so, and it's fun!

VIDEO

The most common form of video transmission is television. In addition to the broadcasts in the typical television band, special slow-scan television (SSTV) is also broadcast in the amateur radio bands. SSTV is different from regular TV in that the commercial TV broadcasts are actually Fast-Scan TV. SSTV is different from FSTV because the scan rate is much slower. That means that the screen is updated at a much slower pace than regular TV. As a result, SSTV is much more useful to transmit still images than moving images. Like the other forms of amateur

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radio, only noncommercial, two-way communications can be transmitted, so don't expect to watch your favorite show on the SSTV frequencies. In order to send and receive SSTV signals, you would need a TV or TV monitor, a scan converter, and camera, in addition to an HF SSB transceiver.

One mode that is somewhat of a cross between a digital and a video mode is facsimile (fax). For most people, faxes were born in the 1980's; however, radio faxing goes back to the late 1920's, when the mode first experiments were taking place. Several years later, fax services, such as a special radio fax station that only transmitted the New York Times, were active. Like the standard telefax machines, radio fax sends the data line by line until

the picture is complete. Some amateur radio companies are manufacturing relatively inexpensive modem units specifically to interface with computers and receivers so that you can send and receive faxes via the

HF frequencies.

For more information on data and video communications, check out the annual ARRL Handbook for Radio Amateurs by the staff of the American Radio Relay League, Your Gateway to Packet Radio by Stan Horzepa, The RTTY Listener by Fred Osterman, The Guide to World RTTY Stations and The Guide to Facsimile Stations by Joerg Kingenfuss, The Weather Satellite Handbook by Dr. Ralph Taggart,The Packet Radio Handbook (2nd Edition) by Jon Mayo, and The Amateur Television Workbook by M. Stone.

HF SSB vs. VHF/UHF RADIO COMMUNICATION SYSTEMS

There are many situations in remote areas developing countries where HF systems offer superior performance at a lower cost than VHF and UHF communications systems. HF SSB communications is far more reliable-- especially where mountainous terrain or distances over 14 miles are encountered.

VHF/UHF COMMUNICATIONS

The coverage of this manual is confined to the HF spectrum, but it is important to know about the other radio bands. For example, as you go higher than about 30 MHz, the radio spectrum starts operating a lot more like light; radio signals operate under the "line-of-sight" theory. Instead of being refracted by the ionosphere, as they do at the lower frequencies, signals at the higher frequencies (typically 50 MHz and higher) cut right through the ionosphere and into outer space. This is the same thing that happens when the MUF is low and the signals on the upper regions of the HF spectrum cut through the ionosphere. Because no "skip" can be relied upon (unlike on the HF frequencies), VHF and UHF signals typically do not travel long distances unless the towers are very high and very high powers are used. Although the signals in the regions above 30 MHz can sometimes skip hundreds of miles, this sort of propagation is very irregular and cannot be relied upon.

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Sky Wave signals can bounce several thousand miles off the ionosphere.

Ground Wave signals follow the contour of the Earth--in hilly areas from 1 to

300 miles.

"Skip" is a key to understanding HF radio: at most any time of day, you should be able to transmit a signal to a given part of the world with a relatively small amount of power. Although these long-distance "skywave" characteristics make up the bulk of HF operations, don't ignore the ground-wave function of HF for short-range communications. The "perfect-signal" ground-wave range for HF frequencies depends on the season, the daily propagation conditions, the frequency chosen and the time of day.

Although the moon has been used to achieve great distances under experimental conditions using "moon bounce" VHF and UHF communications, the tracking requirements and the sophisticated equipment required render this type of communications useless for regularly scheduled radio operations.

COVERAGE

HF radio signals (2 to 30 MHz) can be received at distant locations using either ground-wave or sky-wave signals. Ground-wave signals follow the contour of the ground in hilly regions for 1 to 50 miles, depending on

frequency. At distances greater than 50 miles to several thousand miles, sky-wave signals, which bounce off the F2 layer of the ionosphere are involved.

Unlike HF signals, those in the VHF/UHF range do not follow the contour of the ground. Once again, the "line-of-sight" theory comes into play. If you are using a VHF or UHF communications system and are deep in a valley, your signal or that from the

repeater might be blocked by the terrain. Or if you were in a city, tall buildings or other man-made objects could obstruct the signals. In cases such as these, your communications equipment would be rendered useless until you once again were back in the line-of-sight range of the receiving station.

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REPEATERS REQUIRED ON VHF/UHF

Because of the limited distance covered by VHF/UHF systems, most installations require some method of relaying signals UHF/VHF signals to establish reliable communications at significant distance. Typically, radio amateurs, commercial radio operators, and others, use a system of repeaters to relay these signals. A repeater is a transmitter, receiver, and duplexer combination that are connected to an antenna on top of a tall tower.

The first step of repeater operation is to transmit a message via a handheld transceiver that looks something like a cellular phone. The signal from the handheld is received by the receiving portion of the repeater. Then, the output from the receiver is fed directly into the transmitter, which transmits the signal with more power and with a taller antenna. The duplexer isolates the receiver and transmitter and allows one antenna to be effectively used for both receiving and transmitting. Although it might appear that the repeater transmitter would be transmitting continuously (whether or not anyone was being relayed), it's not; the strength of the input turns on ("keys") the repeater's transmitter.

Repeater-type VHF/UHF operations are much more costly than comparable HF systems in many situations. Repeaters require installation on the highest possible terrain, power source, tower(s), and a building to house equipment. This high terrain can cause problems because if no such land is already owned, it must be purchased. Then, a permanent building must be constructed to house the repeater and a power system (probably power lines or a generator power system). In order to construct this system, land (for the repeater site) and a road might need to be cleared. Depending on country, weather (such as high winds and extreme temperatures) can also force changes in the system design.

Aside from the costs, one of the worst aspects of VHF/UHF repeater use is that the locations are vulnerable. In the case of HF communications, the transceivers are taken to each site by the operators. The transceivers and antennas can even be installed in a car or carried in a backpack unit. With a repeater, the portable units are handheld or mounted in a a vehicle, but the repeater site, the most important, expensive, and powerful link in the system, is abandoned and vulnerable to anyone who might want the equipment or the site. Therefore, consider the physical security if you plan to use VHF/UHF repeaters.

You should allocate the same level of security to a critical repeater site as you would give to a critical central telephone exchange or satellite ground station. Your communications are of crucial importance, and a UHF/VHF system is only as strong as the weakest link.

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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA

© 1997 SGC Inc.	P.O. Box 3526, 98009 Tel: [phone] Fax: [phone]

SSB has become the modern choice for communications in general.

NO REPEATERS WITH HF SSB

HF single sideband technology has been a dependable system for more than 50 years in various international communications services on frequencies allocated by the International Telecommunications Union(ITU) for commercial telephone and data services and within individual countries, as permitted by treaty. SSB is the mode of choice by leading military organizations and international airlines, which use HF SSB to keep in contact with units on the move throughout the world.

A typical fixed HF SSB installation consists of a transceiver and an antenna, which could be a short vertical or a 20 to 90 foot wire suspended from a tree or rooftop. Mobile installations use an efficient 9

foot whip antenna. No repeaters are required for communications that range from local to intercontinental.

The range varies, depending on the frequency used. In the daytime, higher frequencies

are used for long-range communications. This is because the F2 layer (one of several major layers) of the ionosphere, which reflects HF radio signals, lowers at night. This daily movement of the F2 layer is also why distant stations can be heard at night on the AM broadcast band.

SECURITY

Single sideband technology requires a more sophisticated receiver to intercept signals than VHF/UHF systems, which use simple FM signals. Although the SSB mode is somewhat common among amateur operators, it inherently provides some security of communication. This is the "cartoon duck" sound (when listening on a typical shortwave receiver) that was mentioned in the first section of this user guide. Also, several different types of scrambling devices (such as the SG-1703 high-security scrambler) are available.

Repeater systems are prone to be misused unless some radio security feature is placed on its input. If others learn of the repeater in the area and decide to use it for themselves, they only have to determine the input (receive) frequency of the repeater and transmit a signal on that frequency. Then, their signal will be re-transmitted by the repeater. Such communications could be used with harmless or malicious intentions.

To avoid these problems, repeaters sometimes have a decoder in the repeater. In this case, a code will be transmitted by the handheld unit before any communications occur. A correct code will turn on the transmitter and allow the repeater to relay the signals.

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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA	© 1997 SGC Inc.
P.O. Box 3526, 98009 Tel: [phone] Fax: [phone]

An 80 AH gel cell battery will provide a healthy mobile operation.

In mobile, a separate battery should be dedicated to the HF-SSB system.

POWER

In mobile HF communications systems, you probably won't even notice that power from your vehicle's motor is being used. That is because your vehicle's alternator is producing a set amount of power, whether or not any

accessories (heater, air conditioning, lights, etc.) are being used. Likewise, even if you are transmitting continuously, you probably won't notice any difference in performance between that and driving without the transceiver.

Regardless, for any portable or mobile HF installation (marine, commercial, amateur, etc.), SGC always recommends that a separate battery (or several) be devoted to the radio system. This works to your advantage in several ways. If the radio needs more power, a second battery is in

reserve. If you need more power to start an engine, reserve from the second battery can be used. Or if you are in an emergency situation with a nonfunctional vehicle, you will have plenty of battery power to transmit for assistance.

INSTALLATION

The base station installation for HF SSB systems is generally quicker than VHF/UHF repeater systems because of the different antennas that are required. An HF wire antenna can be easily hoisted into position with a rope in just a few minutes. On the other hand, VHF/UHF antennas generally require a tall tower to reach an appropriate operating elevation (thus, the new tower, in addition to the antenna, must be installed).

The HF portable antenna systems are typically also simple to install. SGC produces The SGC Quick Mount System (QMS) in conjunction with the SG-230 antenna coupler and SG-303 high-performance antenna allows a mobile vehicle installation within 15 to 20 minutes. This is slightly longer than the 10 to 15 minutes required for a mobile VHF/UHF installation using a magnetic mount antenna. The trade off is the superior range, regardless of terrain and lower initial overall system cost provided by HF SSB.

UHF/VHF magnetic mountings are usually not strong enough for commercial service, thus you might need to drill a hole in the car body. Not only is the Quick Mounting System strong and easy to install, but you can just as easily remove the system and place it on another vehicle.

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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA

© 1997 SGC Inc.	P.O. Box 3526, 98009 Tel: [phone] Fax: [phone]

COST

It is appropriate to consider costs on a side-by-side basis when selecting a communications system for use in a developing country. In addition to the cost chart on the following page, you should also consider the long-term uses for equipment as needs of the country change during development. HF radio equipment used by paramilitary forces can be re-used in public civil services in remote field locations with little expense, other than moving relatively portable HF antennas.

Moving the VHF/UHF equipment will generally involve moving towers, buildings, repeater equipment, the power supplies for the repeaters, and the individual fixed or mobile units. In addition, new antenna height/coverage studies will have to be made to find the best locations for the new repeater sites. Then the land will have to be purchased and the process of clearing land and installing equipment will begin again.

Installation comparison study:

	HF SSB	VHF/UHF
Base Stations Available	Yes	Yes
Portable Unit Available	Yes	Yes
Repeater Required	No	Yes
Tower Required	No	Yes
High Elevation Desirable	No	Yes
Repeater Building Needed	No	Yes

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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA	© 1997 SGC Inc.
P.O. Box 3526, 98009 Tel: [phone] Fax: [phone]

Cost Comparison Study:

Three base stations, each 50 miles apart, need to be in communication in hilly terrain. The following would

likely apply:

	HF SSB			VHF/UHF
3	Transceivers	$6,000	3	Transceivers	$	6,000
3	Antennas	$1,350	2	Repeaters	$	9,000
3	Antenna Masts	$300	5	Towers	$	9,000
			2	Repeater Sites	$	??
			2	Repeater Bldg.	$	4,000
			2	Repeater Power	$	6,000
TOTAL		$7,650	TOTAL		$	34,000 + site cost

As you can see in this type of installation, HF SSB has a tremendous cost advantage over VHF/UHF

alternatives, where long distances (over 12 miles) are involved.

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The SGC Building, 13737 S.E. 26th St. Bellevue, Washington 98005 USA

© 1997 SGC Inc.	P.O. Box 3526, 98009 Tel: [phone] Fax: [phone]