I think it was Orson Wells who had a commercial that said "No wine
before its time." Do your antennas age like fine wine? Mine do. Have
for years and years. Well, at least they need a few days aging.
I've been playing with antennas for a long time. When my Dad died two
years ago, I went out in his yard and there she was, my dipole antenna
still strung between two trees, just like I had left her 50 years earlier.
I have 9 antennas. A 70 ft random wire, a 400 ft long wire, a G5RV, a
20 m dipole, 20m Hamstick, 10m vertical, 15m vertical, Hustler 4 BTV,
VHF discone, etc etc. No beams (yet.) After cutting, erecting, playing
with an antenna, I start the measurement game, using either an MFJ-259B
or Palstar ZM-30 antenna analyzer. After a million iterations, trips up
the ladder, on the roof, etc, I get it as good as I can get it. But
wait! We're about to make a "swell gal sweller." You see the next day,
my numbers have changed. Usually for the better. I've noticed this
phenomena for years. Over a few days or even a week or two, the antenna
seems to "settle in." -- "the final numbers can be dramatically
different from the first. In fact, I've learned not to cut, close up,
stow my gear for a few days until this settling takes place.
I had this happen again over the past few days reminding me of this
phenomena. Has no one else noticed this?
My Hustler 4BTV suddenly had a high SWR. Troubleshooting lead to a
burned connector in the coax that had resulted in a dead short. I took
the antenna down, repaired the damage, checked everything out,
reinstalled it, and ran the numbers. Before this episode, the
40/20/15/10 meter SWRs were: 1.4 / 1.6 / 1.8 / 1.1. After reassembly
and reconnection of leads and radials, the numbers had all jumped to
over 2.0 - some over 3.0 I wanted to use this antenna for 20m on this
weekend's contest, so after a whole lot of finagling, I got 20m down to
about 2 - 2.2. I used the antenna for a while at reduced power on
Friday nite. On Saturday morning, the SWRs had fallen into
"operational" areas, but still high. I used the antenna normally all
day Saturday. By Sunday morning, the SWRs had fallen more - to 1.2 /
1.6 / 1.7 / 1.1 - I'm better off than before!
As I've mulled this, I hypothesized that putting RF through the lines
and the antenna had burned out moisture and eliminated areas of high
resistance on mating antenna and connector surfaces. But wait - I've
had this "next day improvement" on antennas that had never been fired
up. And, on my 400 ft long wire which has no connectors - it runs
directly to a 4:1 balun next to my radio. This antenna, which is up 40
ft in the trees was a big disappointment when I installed it. But over
a period of weeks, indeed months, it's SWRs continued to improve, as did
it's on-the-air performance. It truly was "mellowing" and aging
gracefully. I was picking up entire bands that were unusable at the outset.
I'm totally convinced that this is a real phenomena, albeit one I do not
understand. I have both of Ward Silver's antenna comparison books, and
I have often wondered whether the performance figures derived from tests
performed a short time after an antenna was installed and hooked up,
would be accurate the next day, or the day after.
Just a little empirical knowledge gained over years of playing around
with antennas while my hair turned white.
Comments anyone?
Bob
W7DDD
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