Atlas 180 Service Manual

INTRODUCTION

The Atlas 180 Transceiver is designed for single
sideband and CW communications in the 20, 40,
80 and 160 meter amateur radio bands. It employs
all solid-state circuitry, with modular construction.
Its conservative 180 Watt power input rating will
provide world-wide communications from fixed,
portable or mobile installations.
Atlas Radio Inc. is licensed by Southcom
International, Inc. of Escondido Calif.,
manufacturers of military and commercial radio
equipment. With this agreement Atlas Radio is
able to bring the most advanced, state-of-the-art
circuit designs to the amateur radio market. Les
Earnshaw, founder and director of R & D at
Southcom is considered to be one the foremost
solid state engineers in the world, effectively
proven by the rapid growth of Southcom
International in the military and commercial
markets of the United States as well as many
other countries.

The high performance and reliability of
the Atlas 180 is enhanced by the finest
craftsmanship, and a most thorough quality
control program. Our staff is made up of highly
skilled assembly workers, technicians and
engineers, many of whom are radio hams.
Our service department if and when needed, is
dedicated to making every Atlas owner a
satisfied customer. Speaking for all the gang at
Atlas Radio, we wish you many hours of
operating pleasure with your atlas 180.

73 Herb Johnson W6QKI

Pres., Atlas Radio, Inc.

1

TABLE OF CONTENTS

Technical Specifications……. 2,3
Block Diagram……………… 3
Special Circuit Features…….. 4
Photos, Top-Bottom-Rear Views 6,7
Mobile Installation………….. 8
AC Power Supply Console…. 8
Linear Amplifier Connections 9

GENERAL SPECIFICATIONS

BAND COVERAGE: 20, 40, 80 and 160 meters.

FREQUENCY RANGES: 1800-2000, 3500-3850, 3700-4050,
7000-7350, 14,000-14,350 kc.

FREQUENCY CONTROL: highly stable VFO common to both
receive and transmit modes. Tuning dial calibrated in 5 kc
increments with easy interpolation to 1kc. Tuuning rate: 15 kc per
revolution of the tuning knob.

EXTERNAL FREQUENCY CONTROL: Rear socket provides
for plug-in of external VFO or crystal oscillator accessory for
separate control of transmit and receive frequencies or for
networkand MARS operation.

CIRCUIT DESIGN: All solid state, 4 I.C.s, 18 transistors, 32
diodes. Single conversion, 5520 kc I.F.

MODES OF OPERATION: SSB: lower sideband on 40, 80, and
160 meters, upper sideband on 20 meters with SB selector switch
in NORM. position. Opposite with switch in OPP. Position. CW:
offset frequency in transmit mode.

MODULAR CONSTRUCTION: Includes plug-in circuit boards
for ease of maintenance.

PLUG-IN DESIGN: Transceiver plugs into deluxe mobile bracket,
or into the AC power supply console, making transfer or removal a
simple operation. All connectors are standard: SO-239 antenna
jack, ¼ in. phone jacks for Mic., CW key, external speaker or
headphones, and linear amplifier control.

POWER SUPPLY REQUIREMENTS: operates directly from 12
to 14 volt D.C. source with negative ground, (standard automotive
system). Current drain is 300 to 500 ma. in receive mode, 16 amps
peak in transmit mode. Atals models AR-117 and AR-230 power
supply consoles are available for AC operation.

FRONT CONTROLS: Tuning Dial, Dial Set, Function Switch,
Band Switch, A.F. Gain, R.F. Gain, Mic. Gain, Sideband Selector,
Calibrator On-Off, Dial Light Dimmer.

FINISH: black vinyl covered steel cabinet, anodized aluminum

panel.

Operation…………………… 9,10
Antennas, Impedance Matching 11
Antennas, Mobile…………… 12
PC-100, PC-200 Schematics... 13
PC-300, PC-500 Schematics 14
PC-400, PC-600 Schematics 15
PC-800, PC-900 Schematics 16
Voltage Chart… Inside Rear Cover
Chassis Schematic… Insert

RECEIVER SPECIFICATIONS

CIRCUIT DESIGN: Front end design provides exceptional
immunity to overload and cross modulation, matching or out
performing the best vacuum tube designs. Signals are converted
directly to the 5520 kc I.F. without preamplification. Converter and
product detector are double balanced diode rings. I.C.s are
employed in the I.F. and A.F. stages.

SENSITIVITY: Requires less than 0.3 microvolts for a 10 db
signal-plus-noise to noise ratio. (typically 0.2 microvolts)

SELECTIVITY: Crystal ladder filter, 8 poles. Bandwidths: 2.7 kc
@ 6 db, 4.3 kc @ 60 db, 9.2 kc @ 120 db !! Ultimate rejection
more than 120 db !! Shape factor: 1.6

IMAGE REJECTION: More than 60 db.

INTERNAL SPURIOUS: Less than equivalent 1 microvolt signal.

AGC CHARACTERISTICS: Audio output constant within 4 db
with signal variation from 5 microvolts to more than 3 volts.

OVERALL GAIN: Requires less than 1 microvolt signal for 0.5
watts audio output. (CW carrier, 1000 cycle heterodyne)

AUDIO FIDELITY: 300 to 3000 cycles, plus or minus 3 db.

AUDIO POWER: 2 watts to a 3 ohm speaker with less than 10%
distortion.

INTERNAL SPEAKER: 3 inch, 3 ohm, 0.68 oz. Magnet. Rear
jack permits plug-in of external speaker, or high impedance
headphones. When transceiver is plugged in to the AC power
supply console, internal speaker is disconnected automatically, and
front facing speaker on console becomes operative.

METER: Reads S units from 1 to 9, plus 10 to 50 db.

CALIBRATOR: Provides 100 kc check points for accurate dial
setting.

DIMENSIONS: 9 ½ in. (24.1 cm) wide, 3 ½ in. (8.9 cm) high, 9 ½
in. (24.1 cm) deep, overall.
Weight: 7 ½ lbs. (3.4 kg) net. 9 lbs (4.1 kg) shipping weight.

2

TRANSMITTER SPECIFICATIONS

CIRCUIT DESIGN: Broadband design eliminates transmitter
tuning. Single conversion from I.F. to output frequency produces
minimum spurious and mixing products. 2 section low-pass filters
on each band provide harmonic suppression equal to commercial
standards. Includes ALC and infinite SWR protection.

FREQUENCY CONTROL: Internal VFO automatically transmits
on exactly the same frequency that is being received. Rear socket
provides for plug-in of external VFO or crystal oscillator accessory
for separate control of transmit and receive frequencies, or for
network and MARS operation.

POWER RATING: 180 watts P.E.P. input, and CW input, (with 50
ohm resistive load and 13.6 volt D.C. supply). Power output: 80
watts minimum P.E.P. and CW (100 watts typical).

EMISSION: SSB: Lower sideband on 40, 80, and 160 meters,
Upper sideband on 20 meters with SB selector switch in NORM.
position. Opposite with switch in OPP. Position. CW: Offset
frequency.

UNWANTED SIDEBAND: More than 60 db down at 1000 cycles
A.F. input.

CARRIER SUPPRESSION: More than 50 db down.

THIRD ORDER DISTORTION: Approximately 30 db below peak
power.

SPURIOUS AND IMAGE OUTPUT: More than 40 db below peak
power.

HARMONIC OUTPUT: More than 35 db below peak power.

CW KEYING: Manual send-receive. Semi-break-in with CW
accessory installed in AC power supply console.

TRANSMIT CONTROL: Press-to-talk with Mic. Button, or
manual transmit with function switch on front panel. Automatic
voice control when VOX accessory is installed in AC power
supply console.

MICROPHONE: Dynamic or crystal. Plug requirement: standard
¼ in. diam. 3 circuit phone plug.

AUDIO FIDELITY: 300 to 3000 cycles, plus or minus 3 db.

METER: Reads power amplifier collector current, 0-16 amperes.

LINEAR AMPLIFIER CONTROL: Rear jack provides for keying
of linear, and ALC control from linear.

3

SPECIAL CIRCUIT FEATURES

The Atlas 180 employs several unique features in its
circuit design which lead to exceptional performance.
Most of the circuitry is directly descended from similar
equipment manufactured for military and commercial
markets by Southcom International, Inc. of Escondido
California. Operating under license from Southcom, Atlas
Radio has access to the very latest state-of-the-art circuit
designs which have been tested, proven, and type
accepted fro military and commercial use.

Receiver input circuit:
Referring to the block diagram, notice that there is no
preamplification of the signal. After passing through input
tuning circuits the signal is coupled directly into a double
balanced diode ring mixer where it is heterodyned to the
5520 kc I.F. Thus, the overload and cross modulation
problems commonly encountered with an RF amplifier
stage are largely eliminated. This has always been
somewhat of a problem with vacuum tube R.F. amplifiers,
and a much more serious problem with transistor or
F.E.T. amplifiers. With its advanced front end design the
Atlas 180 will continue receiving signals in the presence
of extremely strong adjacent channel stations that would
overload, cross modulate, or desensitize other receivers.

Sensitivity: As with most new developments in
technology, it may be difficult to accept the fact that a
proper receiver can exhibit good sensitivity without a
stage, or more, of R.F. amplification prior to frequency
conversion. The fact is that the Atlas 180 is at least as
sensitive as the best of the tube or solid state receivers
having R.F. amplifiers. This is due largely to the very low
noise figure of the double balanced diode mixer, followed
by a low noise I.F. amplifier. Sensitivity is rated at 0.3
microvolts for a signal-plus-noise to noise ratio of 10 db.
Typical measurements will read 0.15 to 0.2 microvolts.

Seelctivity: Following the low noise first I.F. amplifier,
the signal passes through the crystal lattice filter, a highly
sophisticated package designed specially for the Atlas 180
by Network Sciences Inc. of Phoenix Arizona. Here is
where superior selectivity has been tailored to take full
advantage of the extremely wide range of signal levels
that the front end design is capable of handling. A 6 db
bandwidth of 2700 cycles was carefully selected to
provide audio response from 300 to 3000 cycles in both
receive and transmit modes. While occupying slightly
more bandwidth than a 2100 or 2400 cycle filter, it has
been convincingly proven that the transmission and
reception of the audio frequencies between 2400 and 3000
cycles provides a substantial improvement in weak signal
readability.

At the same time, the improved fidelity of voice
communication is readily noticeable.
The 6 db bandwidth of 2700 cycles is backed up
by a 6 to 60 db bandwidth ratio of only 1.7 (shape factor),
and ultimate rejection greater than 110 db. It is this
extremely steep skirt selectivity which will reject strong
adjacent channel signals.

Oscillator switching: The unique method of changing
from receive to transmit mode by switching the carrier
oscillator and VFO is illustrated in the block diagram.
This new development is responsible for great
simplification of the transceiver circuit, leading to fewer
components, lower cost and greater reliability.
In receive mode the first mixer heterodynes the
antenna signal with VFO injection. In transmit mode the
first mixer functions as a balanced modulator with carrier
oscillator injection and mic. amp. input. In both modes the
first mixer output is at the intermediate frequency (I.F.) of
5520 kc.
In receive mode the second mixer functions as a
product detector with carrier oscillator injection. Its
output couples audio frequencies to the receiver audio
system. In transmit mode the second mixer heterodynes
the I.F. signal with VFO injection. Its output is now at the
transmit frequency, and is coupled through tuned circuits,
preamplifiers, driver stage, and power output amplifier.
Oscillator switching is accomplished with four
F.E.T.s resulting in very low intercoupling between
oscillators.

Transmitter Broadband Circuitry: The amplifier stages of
the transmitter provide full power output over the entire

1.8 to 15 mc range, and require no tuning. Tuned circuits
between the second mixer and the transmitter amplifier
module select the desired mixer product and reject the
unwanted products. These tuned circuits are band
switched and provide full coverage of each band. They
are double tuned and over coupled, requiring no further
adjustment after being factory set.
Harmonic output from the power amplifier is
suppressed by a band switched two section low pass filter.
This filter is connected between the power amplifier
output and the antenna terminal. The low pass filters and
power amplifier are both designed for a 50 ohm load. It is
important that the load be quite close to 50 ohms, non
reactive, in order to operate at full rated power.

Receiver Broadband Circuitry: The receiver input filters
are band switched, and provide full band coverage
without need for a panel peaking control. In addition, the
signal passes through the low pass transmitter filter,
suppressing possible interference from strong local VHF
signals.

4

5

MOBILE INSTALLATION

PRELIMINARY NOTES: The D.C. electrical system in an
automobile may at times generate high voltage transients; spikes
of voltage superimposed on the 12-14 volt D.C. system. These
transients may be caused by faulty brushes in the starter motor,
alternator or generator, or loose wiring, and can represent a
possible hazard to the semiconductors in the transceiver. For this
reason we strongly urge that you read the following notes and
follow them carefully:

(1) Clean the battery terminals and clamps, and tighten the

clamps securely.

(2) Tighten battery cable terminals where they attach to the

engine.

(3) Inspect battery cables and terminals for corrosion or

wear. Replace them if they look questionable.

(4) Check battery condition frequently, especially when it

approaches its warranty age limit. Use a protective
silicone grease on the terminals to inhibit corrosion.

(5) Check the alternator and regulator connections for

tightness. Also primary ignition wiring, horn wiring,
lights etc.

(6) Measure the charging voltage from the alternator with

the engine running at about twice idling speed. Voltage
at the battery terminals should measure 13 volts
minimum, 14.5 volts maximum. Consult your auto­electric service shop if correction is required.

D.C. BATTERY CONNECTIONS:
See Addendum Note (3)

The illustrations show how the transceiver can be hung under the
dash, or mounted over the transmission hump. Each installation is
different, so this must be left to the individual. Consult your
dealer or friends with mobile experience if need be. The brackets
can be cut easily and bent as required. The smaller #6 x 3/8 in.
screws are for attaching the brackets to the sides or bottom of the
transceiver. They will replace the #4 x ¼ in. screws that came in
the transceiver, thus allowing for the 1/8 in. thickness of the
bracket. The #6 screws will make the brackets more secure than
the original #4s would. The #10 screws are for securing the
brackets to the underside of the dash, or to the transmission
hump.

6

NOISE SUPPRESSION

The subject of suppressing automotive ignition and alternator noise
is beyond the scope of this instruction manual, so it will only be
mentioned briefly.

Many cars will create very little interference in the HF
bands covered by the Atlas 180. Almost all cars now use
resistance type ignition wire, and will probably create very little
ignition noise. More likely the high pitched whine from the
alternator will cause more trouble. Refer to the various amateur
radio handbooks, available from your dealer, for information on
noise suppression. It will usually be found in the mobile chapters.
Estes Engineering Co., 543 West 184th St., Gardena,
Calif., 90248, manufactures an excellent line of suppression kits
which can help cure the more stubborn cases. It is quite likely that
your dealer also sells the Estes Engineering line.

DELUXE PLUG-IN MOBILE MOUNTING KIT:

This kit includes: (a) 6 ½ ft D.C. power cable with 20 amp in-line
fuse and transceiver plug. (b) Black anodized plug-in housing. (c)
Two 9 in. and two 12 in. black anodized aluminum mounting
bars. (d) 3 in. wide rear brackets. (e) Three #10 x 1 in. sheet metal
screws, and two 8-32 bolts, nuts, and washers

Refer to the illustrations for typical transmission hump and under­dash mounting arrangements.

(1) The rear bracket(s) should be angled as straight back as

possible in order to give good support for pushing and
pulling the transceiver in and out of the mount.

(2) The mounting brackets must be cut and bent to suit the

installation, each case being unique. Try different

positions and select the one for best ease of operation,

and least interference with automotive controls. Then

carefully measure each bracket for length and angle of

bend on its foot.

(3) Remove the acorn nut and hex nut. Slip bracket over

screw, and replace only the acorn nut.

(4) Secure brackets to car with #10 sheet metal screws.

Tighten screws and nuts securely.

(5) Connect 52 ohm coax. cable as illustrated.
(6) An external speaker may be connected as follows:

Locate the speaker plug on the back of the mobile

mount, just above the mic. Plug. Clip out the wire

jumper going from the tip lug to the ring lug. This will

disconnect the internal speaker. Connect the external

speaker from the tip lug to the ground lug.

INSTALLING D.C. POWER CABLE:

The power cable should be run from the transceiver, through the
bulkhead, and connected as close to the battery as is practical.
The best way is to connect directly to the battery posts. Drill and
tap into the lead terminal posts for 10-32 machine screws, and
secure #10 terminal lugs under these screw heads. The
advantage of doing it this way is that even if the battery clamps
work loose, it will not affect the transceiver connections, and the
danger of intermittent transient voltage spikes will be reduced.
If drilling and tapping the battery posts is not practical,
then connect the cable to the engine end of the battery cables.
The negative cable will usually be found going to a bolt on the
engine block, while the positive cable usually goes to a bolt on
the starter solenoid. Install terminal lugs at these points for
connecting the power cable.
The red lead goes to positive and the black to
negative. A protective diode is built into the transceiver plug and
will blow the in-line fuse if polarity is inadvertently connected
wrong.
As discussed in Preliminary notes, the battery clamps
should be cleaned and tightened. All electrical connections
should likewise be checked and tightened.

OPTIONAL SAFETY FUSE:

The D.C. power cable has a 20 amp. in-line fuse installed close
to the transceiver plug. This is a convenient location, but is not
always the best. A more proper location is to install a fuse close
to the battery end of the power cable. There is always a
possibility of short circuiting a cable to ground, either by having
a bulkhead cut through the insulation, or getting pinched
somewhere. With 12 gauge wire and no fuse at the battery end,
the short circuit could start a fire very quickly. A second in-line
fuse, fuse block, or circuit breaker may be installed near the
battery if you’re a worry wart. Otherwise, install the cable
carefully, using tape, grommets, and plastic cable clamps where
necessary.

7

more. An excellent choice is the Sure 404C hand

must be disabled. Refer to instructions that come

MODEL AR-117 and AR-230 POWER SUPPLY SPECIFICATIONS

** INPUT VOLTAGE: AR-117: 117 volts AC,
AR-230: 117 or 230 volts AC, (switch selected).
Both models 50-60 cycles.

** INPUT POWER: 10 watts average, Receive.
250 watts Transmit peak.

** OUTPUT: Low current line: 13.6 volts regulated ½
amp.High current line: 13 volts at 16 amps.

** SPEAKER: 3 x 5 in. oval, 1.1 oz. Magnet,
3 ohm voice coil.

** PLUG-IN DESIGN: Transceiver plugs directly into
power supply console, automatically makes connections
for antenna and front facing speaker. Mic. Jack and
headphone jack are brought out to front panel.

AR-117 SCHEMATIC DIAGRAM

** ACCESSORIES: Space under transceiver permits
addition of VOX unit. Space in rear permits addition of
semi-break-in CW/sidetone unit.

** FINISH: Textured vinyl bonded to steel, durable and
scratch resistant

** DIMENSIONS:
15 ½ in. (39.4 cm) wide.
5 5/8 in. (14.3 cm) high.
9 ½ in. (24.1 cm) deep.

** WEIGHT: 17 lbs. (7.7 kg), less transceiver. 20 lbs.
Shipping weight.

MICROPHONE CONNECTIONS

The microphone may be either a dynamic or
crystal type. If a dynamic is selected, it should
preferably be the high impedance type. A low
impedance mic. will work, but will require
higher setting of the Mic. gain control, and may
require closer speaking.

The choice of microphone is important
for good speech quality and deserves careful
consideration. Select a high quality mic. with
smooth response from 300 to 3000 cycles or

8

mic.

PLUG CONNECTIONS: The plug required is a
standard ¼ in. diam., 3 conductor type. The tip
connection is the keying circuit for the press-to­talk, the ring connection is for the shielded mic.
lead, and the sleeve or barrel is the common
ground terminal.

VOX OPERATION: Most press-to-talk
microphones are short circuited when the button
is not pressed. For VOX operation this feature

with the mic. Open the case and locate the
switch contacts that short the mic. circuit when
the button is not pressed. Either disconnect the
leads or bend the contacts so they do not make.

ATLAS 180 OPERATION

CONTROLS:

POWER SUPPLY ON/OFF, MOBILE: The function switch
has an OFF position which turns off the DC power supply to
the low current circuits. The high current circuits, (driver
and P.A.), remain connected to the DC supply line, but arew
automatically biased off when the low current line line is
turned off.

POWER SUPPLY ON/OFF, AC CONSOLE: The AR-117
AC console has an On/Off toggle switch which turns off the
AC supply line. This switch should be used rather than the
function switch OFF position.

FUNCTION SWITCH: First position is OFF for mobile
operation. “REC” position places the 180 in receive mode.
Press-to-talk and VOX circuits are operative in this position.
“TRANS” position switches the 180 into Transmit Mode in
the event a mic. without a press-to-talk switch is used, or if
you wish to hold in transmit mode without having to hold
the button down. “CW” position is also transmit mode
except that the mic. gain control now becomes a carrier
insertion control and carrier frequency has been shifted
about 500 cycles. (See CW TRANSMISSION).

A.F. GAIN: Controls audio volume in receive mode.

R.F. GAIN: The purpose of the R.F. gain control is to
permit decreasing of the between-speech noise level, thus
providing more pleasing reception. The AGC system in the
Atlas 180 has a tremendous dynamic signal range. With full
R.F. Gain sensitivity will automatically return to maximum
in the absence of a signal, accompanied by a natural
increase in background noise.
You may find it annoying to hear the noise level
increase every time the person being received pauses
between words or sentences. There are really only two
conditions when the R.F. Gain control needs to be on full.
One is when you are scanning the band and want to hear
weak as well as strong signals with about the same audio
volume. The other condition is when you are in a round
table with both weak and strong signals. But, a lot of the
time you can turn the R.F. Gain down a bit, increase the
A.F. Gain correspondingly, and realize more pleasing
reception.

9

BAND SELECTOR AND THE TUNING DIAL: The first
position on the band switch is marked “1.8” for the 1800­2000 kc, or 160 meter band. The upper dial scale is
calibrated directly for this band.
On the other bands the lower dial scale is used. It is
calibrated in 5 kc increments from 0 to 350, and the dial
reading is mentally added to the number on the band switch.
For instance, in the 3.5 position a dial reading of 0
is 3500 kc, a reading of 100 is 3600, etc. In the 3.7 position
a dial reading of 0 is 3700 kc, a reading of 100 is 3800, and
a reading of 300 corresponds to 4000 kc, the upper limit of
the 75 meter phone band. 80 and 75 meters are the only
bands that require a little mental getting used to.
The 40 and 20 meter, (or 7 and 14 mc) bands read
out directly on the dial, with 0 to 300 tuning from 7000 to
7300, and 0 to 350 tuning from 14,000 to 14,350 kc.

PROPER TUNING OF SINGLE SIDEBAND SIGNALS:
Precise tuning of a single sideband signal is very important.
Try to tune exactly to the frequency where the voice sounds
normal. Avoid the habit of tuning so the voice is pitched
higher than normal, and sounds like Donald Duck. This is
an unfortunate habit practiced by many operators. If you
tune for an unnatural high pitch, you will then be off
frequency when you transmit. Chances are the other station
will then shift to your frequency when you are talking, etc.,
and gradually you will move up or down the band. Sooner
or later one of you will accuse the other of drifting….. So,
take the extra care to tune for a natural sounding voice, and
you will then be enjoying the very best quality in voice
communications.

ADJUSTMENTS

TUNING KNOB TENSION: Adjustment has been provided
for increasing or decreasing the torque required to turn the
main tuning knob. Loosen the set screw and remove the
knob. You will find a curved spring washer between two flat
washers on the tuning shaft. Compressing the spring washer
increases the torque. When tightening the set screw, apply
inward pressure on the knob to produce the amount of
tension you want. In home station use you may want no
drag at all, while for mobile use you may prefer quite a bit.

P.A. BIAS: this adjustment is on the back of the heat sink,
and requires a small Phillips screwdriver. Idling current in
TRANS mode should read ½ to 1 amp. Do not measure
idling current in CW mode, as it may give a false reading.
After a period of voice transmission the idling current my
climb to nearly 2 amps., but will drop back when the heat
sink cools. Temperature compensation of the bias supply
prevents thermal runaway.

CARRIER BALANCE: A trim pot. is located on the PC­100 plug in board on the right side of the transceiver. Next
to the trim pot. is a capacity trimmer which is the phase
control. These trimmers should be adjusted for minimum
carrier on the 1.8 mc band.
Connect a dummy load to the transceiver, and measur ethe
output voltage in TRANS mode with the Mic. gain at
minimum. It should null down to a level of 0.1 to 0.15 volts
RMS. Other bands will give a false reading due to oscillator
feedthrough which is not suppressed as much as the carrier.

S-METER ZERO: This is a trim pot. located on the PC-200
plug in board located under the dial drum. It can be reached
with a Phillips screwdriver from the top, just behind the dial
light switch. Disconnect the antenna and adjust the trim pot.
for meter 0.

ALC ADJUSTMENT:

See Addendum Notes (1) and (2)

CRYSTAL CALIBRATOR: The 100 kc calibrator should
be checked every 6 months, or so, against a frequency
standard such as WWV. Aging will cause it to gradually
change frequency especially during the first few months.
The calibrator is on the PC-800 board, mounted on the front
side of the aluminum partition behind the dial drum. A
capacity trimmer in the upper left hand corner is for
frequency adjustment. A test lead may be run from terminal
#1 of PC-100 to the antenna terminal on a general coverage
receiver which is tuned to one of the WWV frequencies:

2.5, 5, 10, or 15 mc. Adjust the trimmer for zero beat when
WWV interrupts their tone modulation.

VOICE TRANSMISSION

Normal operation is with the function switch in REC.
position. Pressing the mic. button switches the transceiver
into transmit mode. Or, if the VOX accessory is installed in
the AC console, speaking into the mic. will switch the rig
into transmit mode.
A TRANS. Position is also provided on the
function switch for locking in the transmit mode, or in case
the mic. does not have a press-to-talk switch.

MODULATION LEVEL is adjusted with the mic. gain
control. When the transceiver is coupled into a proper 52
ohm load, voice peaks will be reaching about 16 amps.,
although the ammeter cannot respond quickly enough to
respond to these peaks. Adjust the mic. gain for average
readings of 5 to 7 amps. Do not run the gain above this
level, or you will flat-top and distort the transmitted audio,
as well as cause splatter up and down the band. ALC will
help reduce this danger, but it is still possible to
overmodulate, so mic. gain must be adjusted carefully.

10

CW TRANSMISSION

The Function switch has a CW position which switches the
transceiver into CW transmit mode. A jack on the back is provided
for insertion of a standard ¼ in. diam. 2 conductor phone plug
coming from the CW key. Keying is accomplished by bias cutoff
of the I.F. amplifier. The keying circuit operates at less than 10
volts positive to ground, and draws less than 5 milliamps., so any
of the electronic keyers will work OK.
In CW transmit mode the carrier frequency is
automatically shifted 400 to 600 cycles. This makes it possible for
one transceiver to QSO another transceiver on CW without having
to constantly tune the dial back and forth. On 160, 80, and 40
meters the transmit frequency is shifted lower than the receive
frequency, while on 20 meters it is shifted higher. The SB selector
switch must be in the “NORM” position for CW operation.
Send-receive changeover must be made with the function
switch, and it may be a bit inconvenient to pass through the
TRANS. position every time. The serious CW operator will want
to install the semi-break-in accessory kit in the AC console. This
item installs in back of the power supply, and includes a sidetone
oscillator with volume, pitch and delay controls.
In CW mode the Mic. Gain control becomes a carrier
insertion control. With key down, advance this control clockwise
until the meter reads 12 amps. This will be 160 watts input power,
(at nominal supply voltage) and output will be about 80 watts.
For novice class operation, insert 6 amps. of carrier for
the 75 watt legal limit.
Adequate ventilation for the heat sink is particularly
important in CW operation, since average power input is higher
than in SSB transmission. Keep a check on heat sink temperature,
and if it is running uncomfortably hot to the touch, back down on
carrier insertion, or make the transmissions shorter.

CAUTION---CAUTION

HEAT SINK TEMPERATURE

The greatest danger to the power output transistors is overheating.
The black anodized heat sink is designed to cool the transistors
adequately under normal operating conditions, but as with any
electronic or mechanical device, it is up the operator to maintain
normal conditions, and not abuse the equipment.
The maximum safe temperature of the heat sink near the
output transistors is about 150 deg. F. This is a temperature that
will be too hot for your fingers to hold, so a good test is to put your
fingers on the fins closest to the transistors. If you can hold on
without a lot of discomfort, you’re OK.
Overheating may be caused by: (a) modulating too
heavily, (b) making lengthy transmissions with short receiving
periods, or (c) restriction of air circulation around the heat sink. If
the air temperature is high, such as on a hot day, or in a hot parked
car, cooling capacity will be reduced. A good rule is to check the
heat sink from time to time, and make certain you’re not running
too hot. Back off on modulation level, or shorten transmission
time. Under abnormal conditions, a small fan may be directed at
the heat sink. This is an excellent idea if SSTV or RTTY
transmission is contemplated.

ANTENNA-TRANSMISSION LINE MATCHING

Proper impedance match between the coaxial feedline and the
antenna system is considerably more important with the
broadbanded solid state amplifier than with tube type transmitters,
which generally have a Pi type matching network. The SWR
should be as low as it can be in order to permit full power
operation. As SWR increases, power output from the Atlas 180
decreases approximately as indicated in the following chart.

SWR Approx. Output

1.0 100 watts

1.1 98

1.2 95

1.3 90

1.5 80

2.0 50

3.0 20

Note: High SWR will not damage the Atlas 180. You may feel free
to operate. Only power input and output will suffer. Reflected
voltage will not cause damage.

AMMETER READING: The ammeter on the Atlas 180 provides
an excellent indicator of impedance match. In CW transmit mode
the Mic. Gain control becomes the carrier insertion control. With a
close match you will be able to run the ammeter up to 12 amps., or
more. (with supply voltage of 13.6 VDC, or 117 VAC)
If you find you can’t run the amps. that high, you can be
quite sure that the antenna is not matched well at that frequency.
Try different parts of the band, and you can tell easily at what
frequency the antenna works best.

INFINITE SWR PROTECTION: The Atlas 180 has a built in
reflectometer which automatically reduces transmitter drive as
SWR increases. This makes the power output transistors nearly
immune to damage from mismatched loads.

ANTENNAS, FIXED STATION

On 20 meters a doublet and most beam antennas will match quite
well across the entire band.
On 40 meters a doublet tuned for phone band center will match
quite well across the band.
On 75 meters the average doublet will have a bandwidth of about
100 kc for SWR of 1.5 or less. To work the entire band with full
efficiency will require an antenna tuner.
On 160 meters an antenna tuner, or at least some kind of matching
system will be essential, since even at resonance it is unlikely that
the feed point will be near 52 ohms.
In any case, it is always best to optimize the antenna system for the
frequency where you do most of your operating.

ANTENNA TUNER OR “MATCH BOX” :
An antenna tuner can be a very useful device to compensate for
antenna mismatch. This may be especially true if you happen to
have a favorite antenna that has been working just fine with the old
tube rig, and now you discover the new solid state rig doesn’t like
the old antenna. Refer to the antenna handbooks for helpful data,
or ask your dealer about antenna tuners now on the market.

Atlas Radio will be announcing a matching antenna tuner about
October 1, 1974.

11

SWR MEASUREMENTS

A bridge for measuring Standing Wave Ratio is very useful, and
strongly recommended for checking impedance match. Use the
following procedure:

(1) Switch the bridge to “Forward” or “Sensitivity”

position.

(2) Set the sensitivity control on the bridge to

maximum clockwise position.

(3) Set Mic. Gain on Atlas 180 to minimum.
(4) Set the 180 function switch to CW mode.
(5) Advance the Mic. Gain until meter on bridge reads

just full scale. (Mic. Gain is carrier insertion control
in CW mode).

(6) Switch bridge to “SWR” or “Reflected” position for

the SWR reading.

(7) Tune the 180 up and down in frequency until you

locate the minimum SWR. This will indicate the
resonant frequency of the antenna, and also the
SWR at that frequency.

(8) Switch the 180 back to REC. mode.

CAUTION: Operate the transceiver in CW mode for only short
periods of time, just long enough to make the SWR measurement.
Check heat sink temperature during SWR tests, and if it is getting
quite warm to the touch, let the rig cool for a few minutes before
continuing.

MOBILE ANTENNAS

The mobile antenna generally requires more critical adjustment
than the home station antenna. This is because it operates over a
more narrow bandwidth, and must therefore be adjusted very
accurately for resonance. Also, the base impedance is seldom very
close to 52 ohms. With tube type transmitters the Pi matching
network will adjust to fairly low impedances, but with a broadband
solid state transmitter, such as is used in the Atlas 180, a close
impedance match is necessary in order to operate at full power.
Various claims about impedances are made by
manufacturers of mobile antennas, but unfortunately our tests on
all the most popular brands indicate that your chances of coming
up with a close match are less than 1 to 10. Average base
impedance is 15 to 20 ohms. Therefore, some method for
transforming the base impedance to 52 ohms is required.

ATLAS MODEL MT-1 TRANSFORMER: This is a broadband
ferrite core transformer with a choice of 4 impedance taps. It
installs inside the car body near the antenna mount. A coax
feedline is run from the transceiver to the transformer and a short
length is connected from the transformer to the antenna mount.
There are taps for 13, 18, 23 and 52 ohms. One of these taps will
provide a low SWR reading. Follow the procedure under “SWR
Measurements”. The MT-1 transformer is available from Atlas
dealers.

CAPACITY MATCHING METHOD: This is an alternate method
for matching to the mobile antenna which works quite well. A
capacitor is connected from the antenna base to ground. This
capacitor is part of an L network which transforms the base
impedance from a low value up to 52 ohms. The small amount of
“L” required is actually “borrowed” from the lower part of the
loading coil.
The capacity value must be determined experimentally,
and will vary from band to band, as well as from installation to
installation.
On 75 meters the capacity will generally need to be in
the 1000 to 1500 picoFarad range.
On 40 meters, 300 to 500 pF.
On 20 meters, about 200 pF.

A variable capacitor can be useful to determine what value is
required. Or a collection of silver mica capacitors, some 100 pFs,
200s, 470s, and a 1000 pF can be paralleled in various
combinations until the SWR comes down to a low figure.
Once you know how much capacity your antenna needs,
it is best to make up a permanent capacitor by paralleling two or
more silver micas. This will divide the R.F. current and reduce the
chances of overheating a single capacitor with too much current.
Follow the procedure described under “SWR
Measurements” when tuning the antenna.

12

PC-100A FIRST MIXER, FIRST I.F. AMP.
C101,108,109,110,112 10nF 100V disc
C102 22pF 10% disc
C103 50pF trimmer
C104,107 2nF mylar
C105 560pF mica
C106 160pF mica
C111 100nF 50V disc
C113 15uF 20V
D101,2,3,4,7,8. 1N4148
D105,6. BA182
Q101 2N3866
R101 100R pot
R102 10K 0.25W
R103,110 4K7 0.25W
R104 330R 0.25W
R105 47R 0.25W
R106,7 1K 0.25W
R108 180R 0.25W
R109 820R 0.25W
L101,2 Trifilar toroid
L103 IF coil
L104 200uH choke

13

PC-200A, SECOND I.F. AMP., SECOND MIXER, MIC. AMP., S-METER AMP.
C201,214 15uF 20V R201,220 2k2 0.25W
C202,3,5,8,9,210,213 10nF 100V disc R202 220R 0.25W
C204,221 100nF 50V disc R203 3K9 0.25W
C206 250uF 15V R204 47R 0.25W
C207 750pF mica R205 27K 0.25W
C212,216,219 1nF 20% disc R206,211 5K6 0.25W
C211,220 2u2 50V R207,212,219 470R 0.25W
C215 6u8 35V R208,221 1K 0.25W
C217,218 22uF 16V R209 68R 0.25W
L201 IF txfmr R213 150K 0.25W
L202,203 Trifilar toroid R214 100K 0.25W
L204 200uH choke R215,217 10K 0.25W
D201,2,3,4,5 1N4148 R216 39K 0.25W
Q201 MC1350P R218 3K9 0.25W
Q202 CA3086 R220 1K s-meter trim

14

PC-300 RECEIVER AUDIO, OSCILLATOR SWITCH BOARD
C301,311 100nF 50V disc R301,4,312 5k6 0.25W
C302,4,7,9,12,21,22,23,24 10nF 100V disc R302 27k 0.25W
C303 220nF 25V disc R303 100k 0.25W
C305 47uF 6V R305 1K5 0.25W
C306,314,320 15uF 20V R306,11,15,19,21,22,24 1k 0.25W
C308,316,319 2u2 50V R307,8,9,17 470R 0.25W
C310 75uF 15V R310 10K 0.25W
C313 47nF 100V R313 1M 0.25W
C315 250uF 25V R314 3K3 0.25W
C317 470nF 100V R316,18,20,23,25,26 6k8 0.25W
C318 22uF 16V Q301 CA3086
D301,302 BA182 Q302 LM380N
D303,4,5,6,7 1N4148 Q303,4,5,6 2N3819
L301 33uH choke

15

PC-400 VFO CIRCUIT BOARD AND TUNING CIRCUITS
C401,2,6,7,9 10nF 100V disc R401,413 27R 0.25W
C403 300pF s-mica R402,3,9,10 10K 0.25W
C404 430pF s-mica R407 22k 0.25W
C405 10pF NPO disc R404 470R 0.25W
C408 1nF disc R405 680R 0.25W
C410 22pF N150 disc R406 15k 0.25W
C411 15pF NPO disc R408 820R 0.25W
C412 15pF N150 disc R411,12 330 0.25W
C413,15,18,21,24 11pF trimmer Q401,3 2N706
C414,16,19 10pF N150 disc L401 3 section osc coil
C417,20 47pF NPO disc L402 3.7MHz cal coil
C422,25 27pF N150 disc L403 14MHz cal coil
C423 68pF NPO disc L404 3.5MHz cal coil
C426 22pF NPO disc
C427 1pF dial set
C428a and b 8pF / sect main tuning

16

PC-500 PRE-AMPLIFIER, DRIVER, POWER AMPLIFIER
C501,2,4,7,10,18,19 10nF 100V disc R515 10k bias trim pot

C503,9 100nF 50V disc R516 330R 0.25W
C505 2nF 600V mylar R517 10R 2W
C506,12,17 100nF 100V mylar Q501 MPS6514
C508,16 15uF 20V Q502 2N3866
C511 2.2uF 50V Q503 PT5766 (TRW)
C513,14 560pF 5% mica Q504,5 CTC A50-12
C515 220pF 5% mica Later Q504,5 CT1601
R501,8,14 1k5 0.25W Q506 2N5490
R502 10R 0.25W T501 toroid transformer
R503,9 470R 0.25W T502 ferrite driver txfmr
R504,13 180R 0.25W T503 ferrite output txfmr
R505 47R 0.25W L501 33uH choke
R506 27R 0.25W L502 1.4uH choke
R507 2k7 0.25W L503 0.6uH choke
R510 470R 0.5W L504 3 ferrite beads
R511 68R 0.25W L505 1.5uh choke/shunt
R512 4x4R7 0.25W parallel D501,2 SI-05

17

PC-600 CARRIER OSCILLATOR, BUFFER AMPLIFIER
C601 200pF 5% silver mica
C602 100pF 5% silver mica
C603 15pF 10% disc
C604,5,6,10,11 10nF 100V disc
C607 50pF trimmer (op SB)
C608 50pF trimmer (norm SB)
C609 10pF 10% disc
C612 520pF 5% silver mica
R601 22k 0.25W
R602 10k 0.25W
R603,6,12 1k 0.25W
R604,5 33k 0.25W
R607 470R 0.25W
R608,13 100R 0.25W
R609 4k7 0.25W
R620,11 15k 0.25W
L601 1.4uH
X601 5523.3kHz xtal (op SB)
X602 5520kHz xtal (norm SB)
D601 BA182
D602 1N4148
Q601,2 2N706

18

PC-800 REC. INPUT TUNING, 100 KC CRYSTAL CALIBRATOR
C801 680pF 10%
C802 50pF trimmer
C803 360pF 5% mica
C804, 5 3300pF polystyrene
C806 270pF 5% mica
C807, 8 680pF 5% mica
C809 4.7pF disc
C810, 13 91pF 5% mica
C811, 12 4-40pF trimmer
C814 0.047uF mylar
X801 100kc xtal
R801 470k 10%
R802 1k 10%
L801 5mH choke
L802 16.5uH coil
L803, 4 1.7uH coil
L805 3.7uH coil
L806, 7 1.4uH coil
L808, 9 1.2uH coil
D801 BA182
Q801 2N3819

19

PC-900 TRANSMITTER INPUT TUNING

C901, 4 820pF 5% poly
C902, 3 37-250pF trimmer
C905 100pF 5% mica
C906, 9 180pF 5% mica
C907, 8 10-80pF trimmer
C910,11,14,16,19 39pF 10% disc
C912,13,17,18 4-40pF trimmer
C915, 20 4.7pF 10% disc
R901, 2 4.7K 10%
L901, 2 2.8uH toroid
L903, 4 7uH toroid

20

C1001, 2, 3 2200pF 5% s-mica
C1005, 7 820pF 5% s-mica
C1006 1300pF 5% s-mica
C1008, 10 430pF 5% s-mica
C1009 680pF 5% s-mica
C1011 330pF 5% s-mica
C1012 220pF 5% s-mica
L1001, 2 2.9uH toroid
L1003, 4 1.8uH toroid
L1005, 6 0.95uH toroid
L1007, 8 0.48uH toroid

PC-1000/1020 LOW PASS FILTERS

21

ATLAS 180 ADDENDUM NOTES:

(1) The ALC CONTROL has been moved to the front panel. It is now concentric with the Mic. Gain control, and is the inner ring

with a black set screw indicating its position.

ALC is the abbreviation for the “Automatic Level Control”, and refers to transmitter modulation level. It aids in preventing over­modulation which causes flat-topping of the power output stages, distortion, and splattering outside the channel.

Full counterclockwise setting of the this control provides no ALC, while full clockwise setting is maximum ALC. Normally a setting
around 12 o’clock will be satisfactory. Some variation between bands may be noted.

By having the ALC control on the front panel, you can utilize its advantages most effectively. Too little control will make it easier to
over modulate, while too much control will limit output power. Try various settings and ask for signal reports until you become familiar
with its effect. If you have a panoramic scanner, this is, of course, the best way to monitor your output signal.

FOR CW TRANSMISSION: The ALC Control should be set to minimum, or full counterclockwise position.

(2) LINEAR AMPLIFIER OPERATION: The illustration on page 9 shows how to connect a linear amplifier to the Atlas 180.

ALC output from the linear may be connected to pin 4 on the AUX. plug.

Special note: The ALC control voltage from the linear must be positive going. Most linears with an ALC output circuit are negative
going. If this is the case with your linear, and you wish to utilize ALC control from the linear, it will be necessary that you modify the
linear ALC circuit. This will usually consist of reversing one or two diodes in order to generate a positive voltage control instead of
negative.

In view of this requirement, you may choose to use the ALC system of the 180 alone. Most linears will operate to the full legal power
limit with little or no distortion.

If ALC control is coupled from the linear to the 180, then the ALC panel control on the 180 should be set to the minimum, or
counterclockwise position.

22

(3) D.C. BATTERY CONNECTIONS: A DELUXE MOBILE MOUNT – (DMK) is available from your Atlas dealer. This plug in

design permits easy removal of the transceiver as all needed connections are made to the mount. All necessary hook up cables
with polarity protection and hardware are part of the mount.

A MOBILE BRACKET KIT – (MBK) – can be purchased for a permanent installation in your car or boat as well as a factory built D.C.
cable – (D.C.C.) with polarity protection and overload protection built in.

IN THE EVENT YOU HAVE NOT PURCHASED THE DMK OR D.C.C., your transceiver comes with two banana jacks for the
positive battery lead, and are to be connected in parallel. The banana plug connects to the negative battery lead.

The battery leads should be of 10 or 12 gauge stranded wire of the automotive type. A 20 amp. fuse or circuit breaker should be installed
in the positive lead.

Caution: It is extremely important that proper polarity be observed. The positive battery lead must go to the two terminals clearly
marked on the back of the transceiver. The negative battery lead must go to the transceiver chassis ground, and the banana plug is for this
purpose. Even momentary connection of the wrong polarity will destroy the transistors, and void the Atlas warranty.

23

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