Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!anaxagoras!ils.nwu.edu!aieta From: aieta@ils.nwu.edu (Michael Aieta) Newsgroups: sci.electronics Subject: RF Interference from Taxi CB's Message-ID: <1491@anaxagoras.ils.nwu.edu> Date: 24 Aug 90 20:13:12 GMT Sender: news@anaxagoras.ils.nwu.edu Reply-To: aieta@ils.nwu.edu (Michael Aieta) Distribution: world Organization: The Institute for the Learning Sciences Lines: 50 Is there any effective way to eliminate interference on my home Musical PA System (Mixing Board, Tape Machine, and Power Amps) 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). All gear fed into the system is connected to the same ground running to a cold water pipe that runs to the bottom of the apartment building (I am on the third floor) and I assume it goes underground somewhat from there. I reduced the lengths of the cables running from the mixer to the amplifiers to attempt to keep them from acting as antennae. It seemed to make a small bit of difference, i.e. the cabbies still come through but somewhat lower and less clear (at least last night they were quieter,although they might have just been farther away. So, down to my questions to you RF,audio,radio,CB,op-amp buffs! How do I shield the cables running from the mixer to the amps? Do you run a twisted pair with a true shield that you attach to a ground at the mixer/pre-amp side only? Both sides? Neither? 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. 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. I have even jotted down plate numbers of cabs that are sporting 20 ft. antennae with fat bases and big coils wrapped around them, and I don't mean to sound prejudiced in any way, but it sure is some coincidence that these airwave pirates all sound (and look when I see the bigass antennae) like either Indians or Arabs - i.e. Paki's. Please no flames from Indians, Paki's, or Arabs, as I am sure there are plenty of plain ol' honky's, Black, and Hispanic, etc. cabbies that are equally offensive to the airwaves, it is just that in my area that is all I hear. Any suggestions, solutions to similar problems?