[TowerTalk] W0IYH Feed line Choke Performance

[Michael Tope]

> >b) to reduce imbalance....
>
> Yes, although that's a tautology.
>
> >c) so that you don't get common mode induced currents
> >coming in from the near field.
>
> OK.
>
> I would add
>
> (d) to keep transmitting RF current from flowing into my house and
> bothering my telephones, alarm system, audio and video entertainment
> systems, computers, etc.; and
>
> (e) to keep QRM and QRN from the electronics etc. in my house from
> being conducted out to my antenna.
>
> -Chuck, W1HIS
>
This sort of goes along with both (a) and (e), but I worth reiterating.
If you are running a horizontally polarized antenna, the choke will help
to reduce the vertically polarized response added by the feedline radiation.
If you are operating in an urban environment, this can significantly
reduce your noise floor as most of the local noise environment is
vertically polarized. I can really see this at my present QTH when
I switch between my 80 meter inverted v and my ground plane on
20 meters. The difference in noise level coming from valley below me
will make your mouth drop. Although much less efficient (its cut for 80
and fed with coax), the inverted-vee almost always produces a
significant SNR improvement over the ground plane, especially during
the day, when the local noise level on the vertical reaches S6 (at night
it drops to something like S3). I am guessing that this day/night
difference is due to the drop in auto traffic and industrial activity
in the valley at night.

73 de Mike, W4EF.......................................