[TowerTalk] Expected VSWR of antenna near the ground

Robert Harmon k6uj at pacbell.net
Mon Sep 28 21:16:20 EDT 2015


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 at 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 at 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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