FM100B • 1
User Manual for Ramsey Model FM100BWT
Here’s the ultimate radio transmitter for any application where a
small, low power transmitter is required! This all-in-one stereo
transmitter has all the features you will ever need for
transmitting a school radio station, around your yard, or even
around the block.
• 2 Line inputs and one mic input-plus a built in mixer!
• Line output for monitoring your broadcast!
• PLL Crystal controlled for rock solid frequency
• Left and right channel peak hold indicators and large LED frequency
display
• Built in power supply, just plug it in! Now operates from 85-264VAC (47 - 63
Hz) without jumpers!
• 1W configuration for operation outside the US!
• Auto AGC microphone muting function for cool talk-overs
• Rugged steel enclosure for years of service
POWER
AUDIO
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Model FM100B
SELF
TEST
SETUP
FREQUPFREQ
DOWN
MIC
AUTO
AGC
LINE 1 LINE 2
MIC
MIC
INPUT
MIC ON
FREQ LOCK
-18
-15
-12
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0
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FREQUENCY
FM100B • 2
RAMSEY TRANSMITTER KITS
• FM100B Professional FM Stereo
Transmitter
• FM25B Synthesized Stereo FM Transmitter
• MR6 Model Rocket Tracking Transmitter
• TV6 Television Transmitter
RAMSEY RECEIVER KITS
• FR1 FM Broadcast Receiver
• AR1 Aircraft Band Receiver
• SR2 Shortwave Receiver
• SC1 Shortwave Converter
RAMSEY HOBBY KITS
• SG7 Personal Speed Radar
• SS70A Speech Scrambler
• BS2 “Bullshooter” Digital Voice Storage Unit
• AVS10 Automatic Sequential Video Switcher
• WCT20 Cable Wizard Cable Tracer
• LABC1 Lead Acid Battery Charger
• IG7 Ion Generator
• CT255 Compu Temp Digital Binary Thermometer
• LC1 Inductance-Capacitance Meter
RAMSEY AMATEUR RADIO KITS
• DDF1 Doppler Direction Finder
• HR Series HF All Mode Receivers
• QRP Series HF CW Transmitters
• CW7 CW Keyer
• CPO3 Code Practice Oscillator
• QRP Power Amplifiers
RAMSEY MINI-KITS
Many other kits are available for hobby, school, Scouts and just plain FUN. New
kits are always under development. Write or call for our free Ramsey catalog.
FM100B PROFESSIONAL STEREO TRANSMITTER USER MANUAL
Ramsey Electronics publication No. MFM100B Revision 1.1d
First printing: January 2002
COPYRIGHT 2002 by Ramsey Electronics, Inc. 590 Fishers Station Drive, Victor, New York
14564. All rights reserved. No portion of this publication may be copied or duplicated without the
written permission of Ramsey Electronics, Inc. Printed in the United States of America.
FM100B • 3
FM100B PROFESSIONAL
STEREO TRANSMITTER
Ramsey Publication No. MFM100B
Price $10.00
TABLE OF CONTENTS
Introduction ...................................... 4
Using the FM100B ........................... 6
FCC Rules and Information.............. 10
FM100B Specifications .................... 19
Warranty........................................... 23
USER MANUAL FOR
RAMSEY ELECTRONICS, INC.
590 Fishers Station Drive
Victor, New York 14564
Phone (585) 924-4560
Fax (585) 924-4555
www.ramseykits.com
FM100B • 4
INTRODUCTION TO THE FM100B
First we will begin with a little history of stereo transmitters at Ramsey
Electronics in order to give you an idea of how we arrived at the development of
the FM100B as our latest stereo transmitter. We have many people call us
each day asking questions about our earlier versions of transmitters such as
the FM25B and the FM10A. Most are questions concerning drifting, sound
quality, and transmitting distance. The tunable FM10A was a great product for a
low-cost entry into the world of micro-power transmitters. The FM25B was the
next step up offering a rock solid, stable frequency just like professional
stations. The latest step was to create a transmitter that not only has a rock
solid frequency, but also all the features you would find in a commercial station.
In answer to customer research and comments, here is the result of months of
design and years of stereo transmitter experience. The FM100B has all of the
features needed to run a professional sounding radio station. It includes
extensive audio filtering to prevent high frequency audio interference, AGC
(Automatic Gain Control) with the microphone to prevent overloading distortion,
a frequency display with easy frequency adjustment, 2 line inputs, 1
microphone input, PLL controlled, CD quality transmission, and more. In other
words we pulled all the stops to bring you a top quality product that will satisfy
even the most discriminating user.
Due to demand from our neighbors down south and wherever else it is legal,
we have included a special component section to give you 1 watt of RF output.
Simply connect a good quality antenna and bingo, you’re on the air for miles (or
kilometers) around.
We are happy to bring you this truly professional product that will give you
many years of fun, reliable use, and enjoyment.
FM100B • 5
ADJUSTING YOUR FM100B TRANSMITTER:
Keep all tests very brief until you have carefully chosen an open operating
frequency in the FM broadcast band.
1. Transmitting Frequency:
After finding a suitable "open" frequency in the 88-108 MHz FM band, adjust
the frequency by first getting the FM100B into setup mode by pressing both
FREQ keys at the same time. Then use FREQ UP and FREQ DOWN keys
until you hear the carrier frequency on a nearby FM radio. No audio input is
needed to make this first adjustment, you can simply listen for a "quieting" in
the normal background noise "hiss."
The modulation sensitivity of your FM100B will vary from one end of the
broadcast band to the other, but not enough to worry about. This is explained
by the characteristic curve of the varactor diode. In order to maintain the
proper 75 KHz deviation, your front panel level control should be set so that
the audio level meters read 0 with an occasional blink or two over that on the
meter. The clipper circuit internal to the BH1415 will prevent overmodulation.
2. Audio Connection:
Hooking up an audio source to your FM100B is really quite simple. However,
there are some general rules:
• A terribly distorted sound is a sign of too much audio level. Simply
rotate the level potentiometers (R42 and R72) CCW to reduce the
level. Make sure you rotate each one about the same amount to
maintain proper stereo balance.
• Stereo LP turntables are low-level output and will require the use of a
preamplifier for proper audio input to the FM100B.
• NEVER connect the FM100B audio inputs to speaker outputs of a high
power stereo system; such a connection will destroy the IC chips.
FM100B • 6
USING THE FM100B WITHIN THE HOME:
A most practical use for the FM100B would be to connect it to the main stereo
system within a large home so that whatever is playing on the main system
can also be tuned-in on portable FM radios in other rooms, the garage or in
the yard. This connection consists of using shielded audio cables to connect
the auxiliary "line audio" output of your cassette deck, CD player or other
stereo device to the audio inputs of the FM100B. Consult the literature that
came with your stereo equipment.
Even if you intend use of the FM100B for your own home and family, it is still
your responsibility (in accordance with Part 15 of the FCC Rules) to ensure
that this operation does not cause interference to your neighbors.
EXPERIMENTAL "BROADCASTING" PROJECTS:
To use the FM100B successfully as a "broadcasting" service to interested
listeners in a school or immediate neighborhood, most of your effort will be
concentrated on smoothly "managing" or mixing the audio signals fed into the
transmitter input. Operation of the transmitter itself consists of the following:
1. Correct construction and adjustment.
2. Carefully checking for an open frequency between 88-108 MHz in
accordance with FCC Rules, Part 15.
3. Setting up a suitable antenna.
4. Connecting the audio source to the Left and Right RCA input jacks.
5. Turning on the transmitter while you intend to be "on the air" and
turning it off when you are finished.
6. For extra protection, use the monitor out RCA jacks to either record
your shows or listen to them on a stereo or on headphones. This will
assure quality sound and transmission. You will need a headphone
amplifier to boost the output of the FM100B to suitable headphone
levels from the line level present at J6.
FM100B • 7
ANTENNA IDEAS:
With the one watt output of the FM100BWT you must use a properly matched
external antenna. It is mounted on the rear F connector.
Ramsey Electronics now offers an antenna called the “Tru-Match FM Broadcast
Antenna”. This antenna has been specifically tested and designed for the FMseries of micropower transmitters and will help you get the most out of these
products. When you call, ask for the TM100 antenna.
A simple, yet very effective, antenna for the FM100B consists of a "dipole" (set
up either horizontally or vertically) connected to the transmitter RF output jack
through a few feet of coaxial cable (either RG-58, RG-59 or miniature RG-174,
available at Radio Shack and other sources). Correct dipole lengths for major
sections of the 88-108 MHz band are:
88 MHz, each side: 2.7 feet; 5.4 feet total
98 MHz, each side: 2.4 feet; 4.8 feet total
108 MHz, each side: 2.2 feet; 4.4 feet total
You can see that there is not a great difference in antenna length from 88 to
108 MHz. Some antenna designers have the view that an "approximate" dipole
such as 2.5 ft. on a side will do fine, while others believe it is worth the effort to
calculate the length for your exact frequency, using the simple formula of
Length (of one side, in feet) = 234/Frequency in MHz.
If the dipole is installed vertically, the end connected to the center conductor of
the coax should be the upper (higher) end. If young children will be around the
set-up, a flexible wire antenna is preferable rather than rigid tubing.
A "ground plane" antenna can be quite effective. A ground plane consists of
one vertical element (the same length as one side of a dipole) connected to the
center conductor of the coax. Four "radials" are connected to the shielded side
of the coax at a 90 to 135 degree angle to the vertical element. The dipole
formula is also used to calculate the length of the radial; since radials should be
slightly longer than the main element, use 240 rather than 234 in your
calculations.
If you are equipped to make the field strength measurements required by Part
15 FCC rules, and you think it would be best to aim or "focus" your signal in a
narrower direction, consult an antenna handbook and design a suitable gain
antenna. See Appendix A concerning FCC field strength limitations. An FMVHF TV receiving antenna could be easily modified for such a purpose.
Ham radio books and magazines are filled with antenna principles and ideas
which can be adapted to your application. Also, you may wish to look at Radio
Shack book No. 62-1083 on antennas.
FM100B • 8
ANTENNA ALTERNATIVES:
If your situation involves a single large building or multi-level home where
reception from the FM100B antenna may tend to be uneven because of walls
and other VHF path obstacles, you might set up the FM100B's output in a
"carrier-current" configuration. If you know how, then do so safely. If not, you
can show your FM100B and this book to a licensed radio engineer and
negotiate with that person for a safe installation which will feed your signal
through interior wiring of your home or building. Do not attempt such an
installation unless you know exactly what to do (and what not to do). Because
such an installation is beyond the original purpose of this kit and the safety
standards intended for all Ramsey kits, we cannot provide further details for
such an installation. Just wetting your whistle a bit!
USING YOUR FM100B
• Setting the frequency:
[1] Press both frequency buttons (FREQ UP and FREQ DN ) at the same
time and hold them in for three seconds to enter the frequency set mode.
The FM100B will confirm your mode selection with 3 short beeps and the
far right decimal point will begin to flash. Note that the far left decimal
point will also flash if the unit is in stereo mode.
[2] Press and hold either FREQ button; the frequency should scroll
accordingly through the valid values.
[3] When you have selected your new operating frequency, press both
frequency buttons again and hold until you hear the triple beep
confirmation. This means the settings have been saved in Flash.
• Toggling Stereo Mode (Stereo / Mono operation):
[1] Press both frequency buttons (FREQ UP and FREQ DN ) at the same
time and hold them in for three seconds to enter the frequency set mode.
The FM100B will confirm your mode selection with 3 short beeps and the
far right decimal point will begin to flash.
[2] Press the auto AGC button to toggle the stereo mode on and off. Note that
the far left decimal point will flash only if the unit is in stereo mode.
[3] When the mode is selected, press both frequency buttons again and hold
until you hear the triple beep confirmation. This means the settings have
been saved in Flash.
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