[Elecraft] Astron RS-35M - Problem Related to RF !!!

[Mike McCoy]

> No doubt you can change the behavior - even stop the shut-down -
> by messing with the antenna, but antennas do not "cause" these
> issues.

OK, I'm going to demonstrate my ignorance here but I'm curious about the
phrase that 'antennas do not cause these issues'

I presently have an RFI related issue with a 87' W9INN MPD5 (80-10) dipole I
just hung at about 30' across the roof a few days ago. Not with the PS but
with a 'hum' emanating from my (powered) PC speakers when I xmit. This 'hum'
occurs ONLY on 20 mtrs.

We're talking a measly 5-10w out here (no K2/100)

Due to (I suspect) a capacitive effect resulting from a close the proximity
to the roof the 20 mtr element is currently resonant around 13.8 Mhz and
thus has a fairly high SWR even at the bottom of 20 mtrs.  The KAT2 easily
handles the mismatch but of course a standing wave current is still present
on the feedline.  Of course this is unacceptable and I will re-tune the
antenna but in the meantime...

"All things being equal" I also have a Sigma GT-5 that is actually
physically closer to the rig/speakers than the dipole but does NOT cause the
speakers to hum when xmitting on 20.  I presume I have no RFI issue with the
GT5 due to an excellent 'in band' match.

Since 'one antenna does and one antenna doesn't' it sure seems to me the
(dipole) antenna is causing an RFI issue.  The coax that is likely actually
radiating the RFI (?) is just a symptom, the effect of a badly tuned antenna
and the antenna is the real source of the issue.  If not the antenna then
what?

Reason I ask is I am *assuming* (and we all know what that means) that since
I didn't have RFI problems prior to this once I get the antenna properly
tuned the RFI will go away.

p.s. This should in no way reflect badly on W9INN antennas. They are really
great. I bought it used and since they are individually custom built I am
simply having to 'tweek' it to my particular circumstance/installation.

Mike 'hope to learn something here' K5PU