Topband: electric fences and Beverage termination
jcclark at wildblue.net
Wed Dec 28 10:56:09 EST 2005
>Date: Tue, 27 Dec 2005 19:56:43 -0800
>From: Paul Baldock <pbaldock at verizon.net>
>Subject: Topband: Beverage resistor triming
>To: topband at contesting.com
>Message-ID: <220.127.116.11.0.20051227194617.03f45508 at verizon.net>
>Content-Type: text/plain; charset=us-ascii; format=flowed
>I put up a beverage about 600ft long today at height between 4ft. to
>6ft. I have a 1:9 transformer (although it actually measured about
>1:11) at the feed end, with both sides of the transformer to the same
> I read in ON4UN's book about adjusting the far end load resistor
>for a low SWR. However I found the lowest SWR is with the far end
>shorted to its ground rod. When the ground it is shorted I get about
>1.4:1, when it is open I get about 2:1 and when it is 500 Ohm I get
>about 1.7:1. I am measuring in the SWR right at the input to the
>transformer with an MFJ259.
>Is the tune for minimum SWR a flawed idea?
>Paul - KW7Y.
Paul et al
A twofer! FENCES AND BEVERAGES
As for the proper resistance on a Beverage termination, you are
looking to maximize front to back. Bill Pfaff, K2GNC wrote an article
on how to find the "right" resistance in one of the ham magazines (I
googled him but couldn't find it but I think it was HR) where he
attached a carbon pot to a kitchen timer and then set it to one hour.
He tuned a station off the back of the antenna and then waited for
the corresponding best F/B by time. He reset the time to the best F/B
and then measured the resistance. He then got a fixed value carbon
resistor and used that value for his antenna.
Bad insulators cause a lot of the problems from electric fences. I
had one almost 1.5 miles away that was creating a raucous noise. The
neighbor is a good friend so they were very amenable to my
investigating their system. I found a number of broken insulators
that were shorting to ground and in the dark, you could see the arc.
There was also grass and other plants touching the wires that were
arcing to ground. Weed killer and a trimmer sold that problem.
As mentioned, there are a number of different kinds of systems in use
including very old relay systems that use an interrupter similar to
what was used for car blinkers and the newer solid state systems. My
neighbor was using an old system but after cleaning up the problems,
that noise source was cleaned up. The newer solid-state systems TEND
to be less offensive but the key to this all, is proper installation.
Too many systems are installed by homeowners that cut
corners.....many never follow RTFM (read the X manual.) We use a
charger from New Zealand designed for use with sheep and it is "noiseless."
One neighbor lost his charger so he hooked up his bug zapper to keep
the pigs in their paddock! That created a lot of noise and if touched
by a pig or child, could have killed them. It also wiped out all
bands but was easy to fix after I explained the "issues" to him.
Happy New Year to all. May we all work the DX we want on topband!
Rural living has it's own set of issues.
73, Craig Clark, K1QX
PLEASE NOTE NEW EMAIL ADDRESS
JCCLARK at WILDBLUE.NET
RADIOWARE AND RADIO BOOKSTORE
PO BOX 209
RINDGE NH 03461
603 899 6957
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