<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>OTOH, 20 watts RF power is a *lot* of power. You can expect you neighbour to not direct that at your house.</div><div><br></div><div>rick</div><div><br>On 28 Nov 2016, at 20:03, Tim Ressel <<a href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a>> wrote:<br><br></div><blockquote type="cite"><div>
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<p>That can help. The mesh size needs to be significantly smaller
than the signal wavelength. In this case we're talking 2 meters,
so a quarter wave is half a meter. Chicken wire is small enough
that it should work. It would not work for something like radar or
microwave ovens (yes, they do leak) where the wavelength is about
30mm or less. <br>
</p>
<p>--tr<br>
</p>
<br>
<div class="moz-cite-prefix">On 11/28/2016 10:55 AM, random variate
wrote:<br>
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<div style="font-family:Calibri,sans-serif; font-size:11pt">Could
a faraday cage like wall of grounded chicken wire mesh help?
(can you tell I'm not an EE?)<br>
<br>
Tim</div>
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<span style="font-family:Calibri,sans-serif; font-size:11pt;
font-weight:bold">From:
</span><span style="font-family:Calibri,sans-serif;
font-size:11pt"><a moz-do-not-send="true" href="mailto:weplar@gmail.com">Tony K</a></span><br>
<span style="font-family:Calibri,sans-serif; font-size:11pt;
font-weight:bold">Sent:
</span><span style="font-family:Calibri,sans-serif;
font-size:11pt">28/11/2016 18:28</span><br>
<span style="font-family:Calibri,sans-serif; font-size:11pt;
font-weight:bold">To:
</span><span style="font-family:Calibri,sans-serif;
font-size:11pt"><a moz-do-not-send="true" href="mailto:oakleylist@btinternet.com">Oakley Sound</a></span><br>
<span style="font-family:Calibri,sans-serif; font-size:11pt;
font-weight:bold">Cc:
</span><span style="font-family:Calibri,sans-serif;
font-size:11pt"><a moz-do-not-send="true" href="mailto:synth-diy@synth-diy.org">Synth DIY</a></span><br>
<span style="font-family:Calibri,sans-serif; font-size:11pt;
font-weight:bold">Subject:
</span><span style="font-family:Calibri,sans-serif;
font-size:11pt">Re: [sdiy] Preventing Radio Ham Interference</span><br>
<br>
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<div class="PlainText">Funny this should come up now, I am
reading my university textbook on analog filter design and
the example I am studying is a ham operating at 30 mhz (
impossible as it's out of band) causing interference to tv
channel 2 , the design calls for 20 db 4 pole high-pass
filter. But that's for radio or tv reception.<br>
<br>
Speaking of interference, I will shut up now;)<br>
<br>
TK<br>
<br>
> On Nov 28, 2016, at 11:14 AM, Oakley Sound
<a class="moz-txt-link-rfc2396E" href="mailto:oakleylist@btinternet.com"><oakleylist@btinternet.com></a> wrote:<br>
> <br>
> Hi all,<br>
> <br>
> My next door neighbour, a keen radio ham, has erected a
new 144MHz directional beam antenna. Unfortunately, for both
of us, when it's pointing towards my house and transmitting,
it interferes with my audio set-up in both my living room
and my little music area. I get on very well with my
neighbour and we've briefly worked together on this so we
know what particular combination of output power, frequency
and antenna choice causes the problem. This antenna mast is
around 5m away from the wall where my audio gear is
situated. When he uses his other non directional antennas
there is no problem.<br>
> <br>
> Anything more than 20W and the RF signal has an affect.
Generally, with my more modern gear it is not a problem, but
my vintage gear (eg. my hi-fi and older synths) are badly
affected. More annoyingly, it's also the modular and my ten
year old Event active monitors.<br>
> <br>
> When transmission is ongoing I hear what seems to be a
loud buzz at 100Hz and harmonics. It's as if the mains is
being gated into the audio pathway during transmission. The
higher the RF output power the louder the buzz. The Event
monitors pick up the noise even with the audio cables
unplugged and the mains additionally filtered. Bizarrely it
also makes the modular and my old SY-1 go out tune but I
can't detect any drop in power supply voltage so I think
it's directly affecting the VCO circuitry.<br>
> <br>
> I think I may have solved it with ferrites on the
loudspeaker cables on the hi-fi but the music area is still
a problem.<br>
> <br>
> At the other end of my house I haven't got an issue but
moving all my gear there isn't really practical - although
I'm thinking about it.<br>
> <br>
> Any ideas? Would some sort of earthed wire mesh fitted
to the wall directly between him and me create a suitable RF
shadow?<br>
> <br>
> Tony<br>
> <br>
> <a moz-do-not-send="true" href="http://www.oakleysound.com">www.oakleysound.com</a><br>
> <br>
> _______________________________________________<br>
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<pre class="moz-signature" cols="72">--
--Tim Ressel
Circuit Abbey
<a class="moz-txt-link-abbreviated" href="mailto:timr@circuitabbey.com">timr@circuitabbey.com</a></pre>
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