Choosing An Operating Frequency - Ramsey Electronics FM10C Manual

FM10C FREQUENCY RANGE SELECTION
Capacitor C18 sets the frequency range of the FM10C. R8 sets the pilot level
for the different bands. Values for C18 and R8 are as follows:
Desired Frequency of Transmission
Lower end of FM band
Middle portion of FM band
High end of FM band
If you are not sure "where" you wish to place your FM transmitter in the FM
band, we suggest you solder an initial "trial" C18 capacitor and matching R8
resistor with a small amount of lead-length to spare, so that they are easy to
salvage and replace. This will enable you to properly test your FM10C and
then at a later point, you may change C18 and R8 as desired.
59. Install C18, either: 15 , 22 or 27 pf (marked 15, 22, or 27).
60. Install R8, either a 180K (brown-gray-yellow), 220K (red-red-yellow),
or 470K (yellow-violet-yellow) resistor.
That's it! But before you grab the power supply and fire up the FM10C,
take a moment to check over your work. Check to be sure that all the
parts are installed and the polarity sensitive ones are placed properly.
Look for solder joints that could be questionable and need a quick touch-
up. Also look for potential solder bridges; the parts layout diagram can
help with that. You may want to hurry and get the kit powered up but any-
thing you find now will save you a lot more trouble later. Unless you like
the smell of smoke and the sound of things exploding! It's worth the few
extra minutes. Looking over the PC board is the first step our Ramsey
technicians complete when testing units here at the shop.
CHOOSING AN OPERATION FREQUENCY
[A] It really is NOT sufficient to just "check" the FM band for an empty fre-
quency, using the FM portable radio closest at hand. It is your responsi-
bility to carefully research what FM stations can be listened to with a good
system within the transmitting range of your FM10C. This is especially
important in the low end of the FM broadcast band (88-92 MHz), where
there are numerous medium power National Public Radio stations per-
haps outside your own town, but which your neighbors may enjoy receiv-
ing, using a good receiver and outdoor antenna. Interfering with such re-
ception is a direct violation of federal law. The most reliable way of finding
a truly open frequency on the FM band is to check the band with a very
good FM receiving system using an external antenna. If you do not have
access to such a radio, most modern car radios (with exterior antenna)
are very sensitive and usable to help you know what stations your
(88-91 MHz)
(90-97 MHz)
(95-108 MHz)
FM10A 16
C18 Value
27 pF
22 pF
15 pF
R8 Value
180K
220K
470K