I agree with John.
On a smaller scale that is what I do. I grew weary of hoisting the
antenna up and down to adjust
the matching so I strung a rope from the tower at 50 feet high and going
out at 45 degrees.
Then I pull the beam up the 45 degree rope with a tram line to about 30
feet above the ground
then back down to adjust. Several times of this and voila zeroed in !
I have tried pointing the beam up etc and never had reliable results.
Takes a little effort to string up the ropes but well worth it.
Up in the final position the beams are always smack on.
Bob
K6UJ
On 9/28/15 5:47 PM, john@kk9a.com wrote:
Have the crane pick it up a ways and check it with your meter. This is done
all of the time. Hopefully since it is a commercial antenna no adjustments
will be needed.
GL
John
-----Original Message----- From: Doug Ronald
Sent: September 28, 2015 14:42
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Expected VSWR of antenna near the ground
Well, okay, I'm convinced, thanks to everyone's advice, that I cannot expect
a VSWR sweep to yield anything meaningful with the antenna on the ground. So
I've done everything I can on the ground to ensure the antenna has been
constructed correctly. I have verified that there is continuity on every
dipole, with the correct phasing to the transmission line. I have verified
that the coaxial transmission line isn't shorted, and has continuity
throughout. Since the antenna is a commercial product, shipped completely
disassembled, I have to assume it will perform when at its design height of
100 feet.
Unfortunately, I'll only get one chance to get it right, since I have to
schedule a crane and helpers, around the constant wind which blows up here
almost incessantly. Judging by the wind forecast, this week is pretty much
out. The antenna is pretty big; 72 foot boom, 105 foot longest rear element,
about 2800 pounds weight, so once I manage to get it up there, its staying
up there. It covers 3 - 30 MHz, although below 4 MHz, the VSWR can rise to
over 2:1. Over the rest of the range the VSWR is < 2:1.
Thanks for all the answers to my question,
-W6DSR
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