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Re: [RFI] Actually an AFI Question ...

To: RFI@contesting.com
Subject: Re: [RFI] Actually an AFI Question ...
From: Kim Elmore <cw_de_n5op@sbcglobal.net>
Date: Thu, 03 Feb 2011 21:18:45 -0600
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
About the only way you can manage that in a straightforward manor is 
with good, old-fashioned AM. Or, alternatively, a two-tone input to 
an SSB transmitter. Both with plenty of power.

But this does remind me of this one time, years ago...

When I was in Colorado, I had a ne'er do well neighbor behind me. 
This guy had been a bit of a jerk in many different ways and he once 
came over to my place with some "muscle" in tow to tell me how much 
RFI trouble I was causing. I happily showed him and his muscle the 
station, handed 'em an FCC RFI booklet, and sent 'em away somewhat 
confused. I never heard much more form him, though I did get a phone 
call or two, always when I wasn't on the air.

Then he got a touch lamp in his second-floor living room, which was 
easily visible from my operating position.

That touch lamp was a pretty sensitive receiver and even at 100W, it 
went completely nuts on 20 m. I use CW almost exclusively then and 
now, but SSB did it in, too. For a long time, he couldn't figure it 
out, but one day I saw him out on his balcony looking carefully over 
at my house. I ducked down out of sight and programmed my keyer to 
send "RFI TEST DE N5OP" continuously at 20 s intervals. I then went 
out and mowed my lawn. He watched me mowing my lawn while his touch 
lamp went nuts and finally went back inside and unplugged it. He 
certainly couldn't accuse me of the problem! I was mowing the lawn!

But that's not the end: I had a good friend over one night who had 
just passed his Tech. I saw my antagonist in his living room, 
watching his TV, with his touch-lamp on.

We grabbed some binoculars and I said "Watch this."

Keeping all lights off, I programmed my keyer with "RFI TEST DE N5OP" 
and fired up my TS-930S. As if my magic, his touch lamp began its 
routine. He got out of his chair and looked at my house. Dark as a 
tomb. He readjusted the lamp and just as he sat down, it started 
again. He did this trick several times and every time, as if on cue, 
it went nuts again when he sat down. By this time my friend was 
almost unable to breathe due to his laughter. But them came the piece 
de resistance: the lamp started its routine again and this time the 
guy leaped out of his chair, grabbed the lamp and shaking it as if he 
were choking it, ripped it out of the wall socket and *threw* it down 
a hallway. Needless to say, that put the poor touch lamp out of its misery.

My friend complained for some days afterward that his sides hurt from 
so much laughing. Mine did, too.

Kim Elmore, N5OP

At 08:56 PM 2/3/2011, you wrote:
>This is obviously not my field, and a bit off-topic, so based
>on no way to acoustically cancel low-frequency sound waves in
>the open (yard) then I have to find a way to motivate the
>miscreants to turn down the volume.
>Which means RF into their sound system to create feedback or
>an acoustic discomfort which causes them to suspect their
>sound system - thus motivating them to turn it down.
>Most vehicles have enough metal left in their shells to be
>RF-resistant, so a high-powered high-pitched audio warble,
>triggered by their noise, seems the best choice.  WDYT?
>One of y'all smart tech-types needs to invent such a critter!
>;-)  doc
> > On 2/3/2011 1:47 PM, doc@kd4e.com wrote:
> >> Can low-frequency audio be canceled using sound?
> >
> > At a single point, like in noise cancelling headphones. Sennheiser and
> > Bose both make some that I would expect to work well.
> >
> >> I seem to recall someone using sound to cancel echos
> >> in a hall to improve the acoustic qualities.
> >
> > That is pure BS.  Sound and acoustics in public spaces is my field, and
> > I can tell you with authority that it is NOT possible.
> >> Would it be possible to detect thumpa-thumpa loud car
> >> audio and transmit sound that would cancel that sound?
> >
> > No.  You could reduce the level substantially in your ears with very
> > good noise cancelling headphones, but most headphones can't produce
> > enough level at very low frequencies to make much of a dent.
> >
> > 73, Jim K9YC
> >
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> >
>Thanks! & 73, KD4E
>David Colburn http://kd4e.com
>Have an http://ultrafidian.com day
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