On Wednesday, December 17, 2014 6:34:22 PM UTC-6, Ralph Mowery wrote:
I have a home buit version of the Carolina Windom. An off center fed
antenna about 120 feet long with a 4:1 voltage balun and from the feedpoint
it goes to an inline ferrite bead choke 20 feet from the feed point, then 80
feet of rg-8 to the shack.

The balun is suspose to be rated for 3 kw. It does have 2 cores in it.
By tests, I know if I run ssb at over 800 watts the balun will heat up and
change the swr.

I have noticed lately that running just 100 watts ssb on 80 meters the swr
seems to be going up to about 2:1 and the rig cuts the power back as
expected as I talk from a starting point of 1:1. That has hapened for the
last two mornings. I don't recall it doing that before. The antenna has
been up for several years. It is just over 1:1 when normal on the frequency
I most often operate on. Today in the afternoon when 80 meters was dead I
transmitted a carrier for about 5 minuits and let off to ID, then another
carrier for about 5 minuits and the swr did not change.

Any ideas why the swr went up for the last two mornings, but did not seem to
go up this afternoon ?


Hard to say really, but sounds sort of moisture related..
Maybe moisture freezing, and then melting, or wet moisture that
later dries out. Just a guess though..
If that balun warms up, it's adding a substantial amount of loss.
Not really related to your problem, but I hate to see perfectly useful
RF turn to heat. :|
Also kind of verifies my theory of the cause of the loss I saw when
using one of those antennas at a field day several years ago.
I had compared it to a regular coax fed dipole, and it was way
down from the dipole.
I always blamed the voltage balun it used, and your experience sort of
verifies that assumption.