Dave gave some good suggestions, but let me add one more. You might be
hearing detected video from a strong TV station. Years ago when I was
testing audio amplifiers for the little "Optimized" transceiver, I was
driven nearly to distraction by that until I finally figured out what it
was. In my case, the headphone wire was the main antenna for the video,
and a good bypass with very short leads right at the headphone jack
cured it. But in your case it could be getting in via the antenna or
power supply leads as well. You can bypass the power supply leads, but
it takes a little knowledge and care to let HF through the antenna lead
while effectively stopping VHF or UHF TV.

Winding the power supply and headphone leads a few turns on ferrite
toroids close to the rig can also be very effective. A good type of
ferrite to use is type 43, which is common, although most other kinds
will work fairly well. You'll probably want to use separate toroids for
power supply and headphone, for convenience. Keep the two conductors
together as you pass them through the core.

Here's how to identify detected video. Hold perfectly still, and see if
the buzz changes. The sound of video will change with the transmitted
picture. If you can correlate the changing sound with the picture from a
local channel, you have the smoking gun. But even if you can't, a buzz
that changes rougness and loudness while you hold still is pretty good
evidence. If you have a 'scope, you can identify video by using line
triggering. Video will look like a pattern that slowly scrolls by,
taking about 20 seconds to drift a full "cycle".

Roy Lewallen, W7EL

Greg Doughty wrote:

Hello to all. I continue to return here as antenna's are the hardest thing to
figure out. We can end the cw argument by testing antenna knowledge hi hi!
Anyways, I have a rock mite 20m qrp that I built and am giving it a go with a
random wire hooked to an mfj 901b tuner. I am using 22 gauge stranded at about
16 feet. The tuner has a ground wire as well. Here is the trick . . . I have
a buzz in the headphones only at certain times. I can move the headphone wire
around and it changes the tone and amplitude of the buzz. In fact it sometimes
goes away all together. However, when I put my hand on the final in the
altoids can, it also lessons it as well as when I put my hand on the can. It
sounds like a ground problem but not sure how to fix it. I tried different
grounds but to no avail. Another problem I am having is the swr meter I have
will not do less than 5 watts(RS) so I am trying to wing it with the tuner and
try to get the highest noise level. Once again though, if I turn the
inductance past d/e I get the hum again. Also if I turn up the antenna
adjustment, the buzz gets worse. I know this is a long one, but I am hoping
someone can help me out.

73
73
Greg