[Elecraft] Audio Distortion on 40mx

[Don Wilhelm]

Dave,

A balun at the antenna along with coax feed does not always guarantee
absence of RF on the outside of the transmission line - the line can couple
with the antenna field and pick up radiation.  If the coax is oriented
perpendicular to the antenna for at least a quarter wavelength, coupling
should be minimized.  Try reorienting your feedline if that is possible.

A transmission line choke or ferrite beads located at the shack entry point
or a quarter wavelength from the antenna feedpoint may be of help - yes that
is in addition to the balun at the antenna feedpoint.

73,
Don W3FPR

----- Original Message ----- 

I have recently reset my K2 and did a realignment of my filters, and now I
have discovered I have some distortion that sounds like RF feedback on my
transmission.  I've had this before when I was running a G5RV, one of my
legs become disconnected and my antenna become unbalanced.

However, I am running dipoles now - with a high quality balun - no chance of
an unbalanced line this time.  My transmission on other bands is perfect,
it's only n 40 that I'm experience the poor audio reports.  I've listened to
it myself and the sound is like a hiss (sometimes a squawk) just after I
modulate.  It's the strangest thing - anyone got any ideas.  I was wondering
if I was getting RF feedback internally in the rig - perhaps from RF flying
around from the ATU?

Any ideas would be appreciated before I spend the next few weeks of my life
on this fault finding tour.