power (ERP) of one watt or less. These regulations are
designed to keep different radio transmissions from
interfering with other radio transmissions (like an “
overpowered” CB radio being received on your TV or PA
system). The FCC levies pretty stiff fines ($10,000 to
$75,000) for violating these regulations which keeps most
Ramsey Electronics’ website says the FM10C
transmitter has enough power to cover “a city” block and
refers the user to the manual for antenna and range info.
The first thing I would try is to check the transmitter
frequency as outlined in their manual on page 14. Modern
digital radios stay pretty well on the tuned frequency,
whereas the analog tuning of the FM10C tends to drift
due to component aging and temperature variations. If the
transmitter and receiver are not tuned close to the same
frequency, there will be an effective loss of the signal by
the filtering action of the receiver.
Next, check the power supply voltage you are using.
The Ramsey specs say the FM10C can operate with a
range of voltages between 5 VDC to 10 VDC. A little
secret: The higher the voltage you operate the transmitter,
the higher the output power which means the longer the
range of reception. If these remedies are not enough, look
at antenna placement relative to the backyard (I assume
that is where most of the time is spent based on your
If the transmitter is hooked to the TV at the front of
the house, there may be enough signal loss due to the
house’s building materials to cause your problems. The
ideal placement of the transmitter using the whip antenna
that comes standard with the FM10C is on a deck in the
middle of the back of the house (I realize audio cable runs
may be a nightmare unless the TV is near a back window).
You could look at using an external FM band antenna
installed in the backyard with as “short as possible”
coaxial transmission line (coax in CB and ham lingo)
between the transmitter and antenna (check with Ramsey
to find the impedance of the antenna so you can match
the coax characteristic impedance to the antenna’s
impedance or there will be a LARGE signal loss). You
should be able to hook the coax shield to the FM10C
antenna ground and the center conductor of the coax to
the FM10C’s signal (the other antenna connection). Make
sure the antenna ground and signal connections are not
shorted together or you will lose all signal power and
possibly damage the FM10C’s power circuits.
The American Radio Relay League (ARRL) website at
www.arrl.org is a good place to start looking for
alternative antennas (which is too lengthy to cover here).
A metal sheet placed about one antenna length behind
the whip antenna would tend to increase the effective
radiated power into the backyard (experiment with
reflector spacing and antenna length/height/tilt for the
best signal coverage).
In the “days of yore” with analog TV a solution, you
would have been able to buy a receiver for the TV FM
audio signal. With the advent of digital TV, I do not know
of any portable audio receivers on the market for TV
My commendations go out to everyone today who
builds electronics kits or devices. Kit or scratch building is
a great way to learn electronics. In this day of “cheap
manufactured” electronic entertainment and instant
gratification, most people have forgotten the technology
that gives them these fantastic devices (philosophy lesson
for the month).
Good luck and let me know how things turn out. NV
16 October 2014
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