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Re: blanking police radio



Original poster: "Scott Bogard" <teslas-intern@xxxxxxxxxxx>

Hello everybody,
I did an experiment once to see just what kind of interferance TCs can cause to radios. I set up a very small spark gap tesla coil, and had a radio (for listening to music or whatever). The radio was 2 feet away from the coil (which did little else other than make corona, as the secondary was 1.5in by 7in). What I found was that it always generated a little bit of interferance in all ranges (AM and FM) but only in the low AM range was any clear definant noise heard (a very loud and suprisingly stable hummmm) once the radio was tuned to the mid and upper AM ranges, the hum turned to an intermitted quiet crackle, which persisted into the upper FM ranges. So I would say unless the Police radio was in the low AM ranges (which it clearly isn't), there is no way a tesla coil could cause a substancial interferance of any kind. But I am no expert, just felt like putting in my 2 cents!
Scott Bogard


From: "Tesla list" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Subject: Re: blanking police radio
Date: Mon, 19 Mar 2007 19:25:07 -0600

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 09:32 PM 3/18/2007, Tesla list wrote:
Original poster: "earl rhodes" <earl_1975@xxxxxxxxxxxxx>

hi all
isnt it possible the report is correct ?? cheap radios suffer serious bleedover from other radio sources !! im not ham i was citizen band ! surely police radio isnt very high quality mor just summat that works !!

Nope.. commercial land mobile radio is required to meet certain performance standards, just to be legally sold. And, then, while the local gendarmes aren't wealthy, they aren't that cost sensitive, that they would cheap out on the radios.



crap!! so does anybody know the frequencys were talking about !!


In the U.S., the police generally use low VHF (30-88 MHz, highway patrol, forest service), high VHF (150-174 MHz), or UHF (400+ MHz) and some 800 MHz trunking stuff these days.

A TC will put out some VHF power (as Terry Fritz measured a decade ago or so), but not all that much. It's also spread over a very wide bandwidth, so even if the total power is high, the power in any one channel is very low.





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