[PLUG] Feedback insanity

[Larry Brigman]

On Fri, Jan 23, 2009 at 4:53 PM, John Jason Jordan <johnxj at comcast.net> wrote:
> On Fri, 23 Jan 2009 09:33:05 -0800
> Larry Brigman <larry.brigman at gmail.com> dijo:
>
>> > Troubleshooting something like this is maddening.
>>
>> Combined ground loop w/radio reception?
>> Is all the equipment plugged in using grounded plugs/receptacles?
>> Anything using 2 prong cords that don't have one side larger than the other?
>
> Well, first off I can say that I am pretty sure it is not a ground loop
> problem. If it was a ground loop wouldn't the frequency be 60 Hz? I
> definitely know what a 60 Hz hum sounds like, and this is way higher -
> around 2K Hz or so.
>
> As for two-prong plugs, everything in the area has three prong plugs
> except the wall warts for the router, switch and modem. And they are
> all polarized. And I wired the outlets myself when I redid the house
> wiring a few years ago. The main panel has separate ground and common,
> and the grounds are connected to two earth poles 20 feet apart, plus a
> water bond.
>
> The wow-ee-wow sound it makes could be from rf. There are a lot of
> electronic things in the room, so the possibility that stray rf is
> being created is very high. Plus, the fact that the volume and pitch
> changes as I move my body around sounds exactly like rf. But what on
> earth could be receiving it and turning it into audio? I get the sound
> even with the receiver turned off. That's the part that has me shaking
> my head.
>
> I did buy some new heavy duty speaker wire today. I've been planning on
> replacing the wimpy stuff that's in the wall now anyway. When I
> finished the remodeling I used 4x8 panels of 1/2 inch particle board
> with screwed on bats instead of sheetrock so that I could open the wall
> again. This wall has a lot of stuff in it - cable connection, for
> example. I'm going to bore new holes for the speaker wires too. I doubt
> that it'll make any difference though.
>
> I'll keep poking at it. I can probably solve it just by repositioning
> things over and over until it goes away. I'm just curious what is
> causing it.

http://www.crystalradio.net/crystalplans/xximages/inventions36aug.jpg
Well a crystal radio doesn't need any power. A speaker with cross-over network
with a diode in it could possibly get somewhere close enough to cause this type
of problem.  Even more probable if you have a high power transmitter close by.

Any Ham radio operators in your neighborhood?