🚀 go-pugleaf

In article <1491@anaxagoras.ils.nwu.edu> aieta@ils.nwu.edu (Michael Aieta) writes:
>
>
>The interference I get is strictly from (what I assume to be highly illegal)
>boosted CB signals from what sounds to me like Pakistani cab drivers in 
>the city.  It can be VERY VERY loud, much louder than any signal coming out
>of my mixer, and it occurs even with the volume from the 
>mixing pre-amp is all the way down.  I have balanced microphones running into
>the mixer (along with line-level signals).  This sum is in turn fed to both
>a tape machine and the power amplifiers through normal 'guitar' cable (1/4"
>2 -wire cable).

A while back on rec.ham-radio, as well in a number of the ham rags, there was
a discussion about cab drivers/dispatchers using the 10/11m CB and ham bands
for their communications.  It seems that when the popular 10m mobile radios
(e.g. Uniden and Clear Channel) came out, the cab companies found that
spending $250 on one of these 25 watt sideband/AM rigs was easier than
paying Motorola or GE thousands of dollars and getting real radios.

>How would I go about putting an RF filter (I have some basic schematics from
>the FCC for TV's, stereos etc.) on my power amps?  On my mixer?  The mixer
>is an Alesis 1622 for you musicians, for you techies it is a monolithic 
>integrated circuit so I don`t believe I can isolate any pre-amp
>components per se.

You can start by putting bypass caps across all speaker leads.  You can
experiment with ferrite chokes on some of the other equipment.  I've had
good luck installing chokes inside equipment such as preamplifiers
and amplifiers in RF equipment.  The same may work in your situation. On the
shielded cables, try some of the popular wrap-around chokes available at
Radio Shack and from most other electronics shops.  You will probably find
only one or two critical paths that the RF is getting in from.  Try coiling
all of your cables into tight loops as close as possible to where they 
connect to any equipment.  In general, try everything until you can narrow
it down.  The problem here is that they aren't always transmitting nearby,
so it will be hard to tell what is or isn't working.

>How exactly do I get these and how do they get broadcast so f%*#ing loud?
>How much power are these guys putting out?  FCC limits are 4W, but it sounds
>to me like these guys are cranking out hundreds.

CB transmitters are 4 watts max AM, 12 watts PEP SSB.  4 watts doesn't
sound like much, but if it's nearby, just about anything with a diode
in it becomes an instant receiver.

Complain to your local FCC field office.  If you have  cab numbers and
companies written down, all the better.  Give them all the info.  Chances
are that you won't see any immediate action, but who knows, they may get
around to checking it out.

Good luck.

								--- Jeff

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Jeff DePolo  N3HBZ             Twisted Pair: (215) 386-7199                  
depolo@eniac.seas.upenn.edu    RF: 146.685- 442.70+ 144.455s (Philadelphia)  
University of Pennsylvania     Carrier Pigeon: 420 S. 42nd St. Phila PA 19104