On 5/27/2021 1:46 PM, Haring family wrote:
What most of the comments you've received probably (or should) mean is that
you don't have a symmetrical/center-fed antenna, so you're more likely to
have feed problems and common-mode problems.
These can be easily dealt with, with a good balun and good common-mode
choke. However, some people will aim for perfection and may ridicule nearly
anything else...
No, they can NOT be "cured" with a common mode choke for several
reasons. First, a choke that could do anything useful to kill common
mode current will likely fry with the severe imbalance, AND with
mismatch to the feedline makes that worse.
Second, to kill RX noise, the choke must be at the feedpoint, not
somewhere down the line.
> I often find it easier for a temporary installation to use an OCFD
> than a fan-dipole. Especially in the trees.
Yes, fans are tough if they need to go through tree limbs, even on their
way up.
> The one I'm planning to use for FD - well, I am skipping 10 meters
and > just planning on 15/20/40. 20 needs a tuner (2:1). 40 is high-1's so
> I'll use a tuner there. 15 has low SWR. That is with the feed at 25%
> of the length.
That's probably fine -- IF the site is quiet, and ONLY if there's no
other station on the same band. But if there are others on that band,
the high common mode and the lack of a choke will cause lots of
inter-station interference.
73, Jim K9YC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|