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[TowerTalk] Aging antennas

Subject: [TowerTalk] Aging antennas
From: Bob Bogash <>
Date: Sun, 04 Mar 2007 13:35:51 -0800
List-post: <>
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?



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