[Elecraft] Non-Resonant Antennas and Chokes

[Jim Brown]

On 1/13/2019 3:42 PM, Al Lorona wrote:
> By the way, whenever Jim says, "...a very good common mode choke at the feedpoint of an antenna...," he means an antenna fed with coax.
What I actually mean is an antenna matched to its feedline at the 
operating frequency(ies).
> For the rest of us, of course, that choke would (should) go at the output of the antenna tuner, whether in the shack or close by.

Actually, for the rest of you, a choke at the shack ONLY reduces 
coupling common mode current into the shack, but does NOTHING to reduce 
noise pickup on the line, because the feedline is not isolated from the 
antenna. Remember -- unless it's choked AT THE FEEDPOINT, that feedline 
is part of the antenna. If it's ONLY choked at the tuner, the feedline 
is a wire dangling from the antenna that isn't connected to anything on 
the other end.

AND if the antenna is not matched, a choke that doesn't fry with TX 
power probably isn't doing anything useful.  For a discussion of this, 
see "Don't Burn Up Your Balun" by retired Antenna Book editor N6BV, from 
QST something like 3-4 years ago.

Bottom line -- if you live miles from anywhere with no noise sources 
pumping trash, all-band non-resonant antennas with open wire feeders can 
be a decent solution -- they transmit just fine if you've done 
everything right. But they're a sitting duck for noise because there's 
no practical way to choke them.

73, Jim K9YC