Hi Gang!

Yup, run into groundloops too. But that usually only occurs when
more than one piece of gear is plugged into more than one side of an
electrical service (3 phase) and an electrical imbalance is present.
Now an open or poor ground is different. However that would create a
LARGE increase in hum and probably would result in a very poor audio
signal received, probably not understandable as close as Dave is to the
receiver with the transmitter. His mic, however will pick up some noise
from his hand picking up the mic, even when it's properly grounded and
shielded. What we have no way to tell is what that hum sounds like and
how loud it is in relation to the actual signal. Most likely, it's
proximity effect as suggested to begin with. I have had some AM
transmitters (Johnson and Heath) that suffered from inadequate power
supply filtering, but even that wasn't really noticeable to a station
even 5 miles away. Extra filtering took care of a lot of it, but it was
still there on a receiver 10 feet away with no antenna.
One thing that wasn't mentioned was the possibility that one of
the cables that interconnect the two pieces of gear, if he has them
cabled up to work as a transceiver COULD have an open shield and that
could account for some introduced hum that gets louder with the audio,
since this is a heterodyne type transmitter, and not a phasing rig.

Kim W8ZV
wrote in message
...
On Jun 22, 3:37 pm, wrote:
On Jun 22, 4:07 pm, "Kim Herron" wrote:

Hi Dave.

Over the years I too have run into the same situation and what the
fellows here are telling you is most likely correct. I can also tell
you the you don't need any antenna to pick up that transmitter when
it's
that close. In fact you'll do better if you don't use an antenna or
something very short to get a better picture of what your xmtr
sounds
like. This is one time where an RF envelope monitor scope comes in
REAL
handy. If you have hum on the transmitted envelope you'll see it on
the
scope.
Kim W8ZV

Thanks, Kim. As recommended by another poster, I think the best
course of action is to use an external antenna and make a few contacts
to get signal reports.

You’re right about the monitor scope. There’s a companion Heakthkit
SB-610 Monitor Scope that I don’t have, but could use right now.

-Dave Drumheller, K3WQ

You mentioned that when you plug in the mic it changes the hum
level,,This may sound too simple,, BUT,,Always bond all items together
(Rec,xmtr,spkr,etc)and to a good earth ground.They used to call it
GROUND LOOPS, I never figured exactly what a groundloop is ,,I do
understand grounding and I hope you have done that first..OK W4PQW
PS (I think a groundloop is when you deliberately wreck your
airplane at the end of the runway just before you kill yourself..)