98 lines
3.9 KiB
Plaintext
98 lines
3.9 KiB
Plaintext
PIRATE RADIO SURVIVAL GUIDE
|
|
Note: this chapter is from the book "Pirate Radio Survival Guide" written by; Nemesis of
|
|
Radio Doomsday, and Captain Eddy of The Radio Airplane. If you like this book and would
|
|
like to support their efforts, you may send a donation of your choice to either Nemesis or
|
|
Capt. Eddy at PO Box 452, Wellsville NY 14895.
|
|
|
|
Please note that some chapters refer to illistrations or drawings, these could not be included in
|
|
this BBS version of the book. If you would like the illistrations or have other questions you
|
|
may inquire at the above adddress.
|
|
|
|
RF FEEDBACK
|
|
|
|
|
|
No matter what you do, RF Feedback WILL rear its ugly head in one form or another at your
|
|
station. Perhaps the only way to avoid RF Feedback is to use a Studio To Transmitter link (STL)
|
|
to get your transmitter away from the rest of the station. Don't worry, you won't have to go to
|
|
that extreme! RF Feedback can be cured 99.99% of the time. All it takes is a little understanding
|
|
of the problem and some tried and true cures.
|
|
|
|
RF Feedback is caused by being in close proximity to a source of High Level RF Energy. It
|
|
doesn't mean that your equipment is really at fault, other than being too darn close! Anything
|
|
electronic is a potential victim for RF Feedback and it will be quite apparent when RF Feedback is
|
|
present!
|
|
|
|
The simplest cure for RF Feedback is the RF Choke. A RF Choke is a coil wrapped around a
|
|
ferrite core to impede the flow of RF Energy. Radio Shack manufactures a snap on unit, it works
|
|
well. A cheaper, and sometimes just as effective, alternative is the ferrite rod from an old AM
|
|
Radio's loopstick antenna. Whatever you can come up with should be used. The key to using RF
|
|
Chokes is in the amount of turns you can use: The more the better. Places to
|
|
use chokes are on the AC Power cords and ALL Audio Cables. Electrical tape helps keeps the
|
|
wraps in place.
|
|
|
|
Another simple way to reduce the possibility of RF feedback is to make sure that any patch
|
|
cords or audio cables are high quality shielded cables. Cheap cables are more trouble than they are
|
|
worth. Also try plugging your transmitter and audio source into different AC outlets.
|
|
|
|
If you still suffer from RF Feedback problems, the next step is to install Bypass Capacitors into
|
|
the effected equipment. I suggest using .01 uF Ceramic Disc capacitors rated at 1000 volts. To
|
|
properly de-RF a piece of gear, you need to concentrate your efforts in two places. First, the
|
|
Power Supply of the unit. Typically, RF will enter via the AC line cord and get into the power
|
|
supply affecting everything else. Open the unit, MAKE SURE IT'S UNPLUGGED! Locate the
|
|
power supply, if you don't know what a power supply looks like you might want to find someone
|
|
who does. Places to install bypass capacitors are on each side of the AC line cord to ground,
|
|
across the Secondary windings of the transformer to ground and finally, across the rectifiers to
|
|
ground. This should clear up any RF getting into the power supply.
|
|
|
|
Should you still suffer, the next step is to bypass all the line in and out connectors on the gear.
|
|
Simply connect your capacitor from the Hot Side (Center Conductor) to the chassis ground. Also
|
|
make sure the equipment is properly grounded in the first place! Do this for all the connectors,
|
|
regardless if they are used or not. And finally, don't forget about your speaker connections, they
|
|
might be bypassed as well since speaker wire tends to act as an antenna!
|
|
|
|
|
|
|
|
If you try all this and you still have problems, try moving the transmitter or antenna farther away,
|
|
sometimes a few feet can make all the difference in the world. You may even have to resort to
|
|
trying another tape deck, some cheap tape decks are impossible to protect from feedback.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|