[PVRCNC] n4cwz antenna question

[Mike Barts]

Dave,
Howie asked the critical question - was it working before? If so, then the
question becomes "what changed"? New UPS? new computer? changes to other
antennas? other changes in the yard?

It could be a break in the shield on the coax creating more common mode
currents to couple into .... everything. I'd start with a careful
examination of the connectors on the coax and the feedpoint. If you don't
have a choke on the feedline, I'd put one where the coax enters the house,
at a minimum, and, preferably, one near the feedpoint. (Yeah, I know, more
weight hanging in the air)

Quick anecdote. Last year for FD, we used the existing antennas at the Corn
Crib, so all the issues were known. Except ... we added an OCFD for a
digital station. This was hung away from the other antennas as much as
possible. We had horrible cross band interference whenever we tried to run
FT8. Think 20/40 sort of interference. Enough so, we pretty much gave up on
digital contacts. Then Sunday morning, Wayne, KU4V in a last ditch attempt
tried adding a choke just below the feedpoint of the OCFD. Voila!
Interference was gone.

Now yours is an RFI issue. But if it's not direct radiation into the device
(UPS in this case), it's a common mode conducted current issue. You may
need chokes on the power lines into/out of the UPS. Putting up a fan dipole
may solve the problem. Or it may just make it different. A choke on the
coax, before it gets into the house, would be my first (baby) step.

73, Mike N4GU

PS. if you need some ferrites, our buddy Howie, WA4PSC, (i.e. the OTHER
Howie) sells them for a good price. Check them out at proaudioeng.com

PPS. Good luck on the knee replacement. On the bright side, you'll have
more time for CWTs and contests for a while.


On Sun, Dec 18, 2022 at 9:35 AM dave collins <davetct at gmail.com> wrote:

> Hi folks,hope everyone is well.  Well i don't know what I did,but my ocfd
> has become unusable because of rfi on 40 and especially 80. Thought It got
> into my pc,but it had gotten into my ups!  I'm wanting to put up a fan
> dipole for 40 and 80. Ordered a balun,so one common feed and I think I will
> be good. Presently I'm using rg8x.  I think its too small for running more
> than a kw. Is it??  I've looked and have seen conflicting info on the web.
> The reason I'm using that is its lightweight . Everything else is lmr 400.
> So,if yall think its too small,what coax do yall use coming from a dipole?
> About 150 ft run. I gotta get busy on this as Im having my first knee
> replacement on the 13th!  thanks and 73 dave n4cwz
>
> --
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