[Antennas] Hy-gain AV-640 issues

[Bob Nielsen]

On Apr 24, 2011, at 11:57 AM, George Frederick wrote:

> Bob,
>  
> A very elderly member of our club had a similar issue with his AV antenna a few years back.  I remember it well as I was a brand new ham and wanted to assist in any way I could.  So I climbed up to the base of his antenna (it was roof peak mounted) to examine the condition of the coax feeder, connector, etc.  Turns out the antenna match box had an aluminum strut at both ends, with a 90 degree bend,  which was screwed to the mast at either end.  The top strut  had cracked at the elbow and it was only noticeable up close.  Opening the match box revealed this strut also was a conductor between the upper mast and the match box output.  Evidently the wind had flexed the mast back and forth for many years before this strut finally parted.  We fabricated a beefier replacement and his antenna has worked fine ever since....!!!!
>  
> 73  George  AF6JT

George, AF6JT, figured it out in an email sent directly to me.

I haven't been feeling too well recently, so didn't have a chance to check out the mechanical arrangement until today (while cutting the grass, which was quite overgrown).  From the riding mower I could see that the upper strut between the matching assembly and the antenna was broken.  Somehow it still presented a reasonable (~3:1) match on 6 meters and I was able to work a local repeater, although the VSWR was quite high on the other bands.  

At least I now know what the problem is.  The antenna has been up for nearly 10 years, so I shouldn't be two surprised.  I'm not looking forward to climbing on the roof (I'm older and less fit that when I put the vertical up), but it shouldn't be too difficult to fabricate a replacement part.

73, Bob N7XY

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N7XY DX Cluster Node - telnet to n7xy.net, port 7300