I suspect that if you used an impedance bridge you would find the antenna is
working as a 5/8 on some freqs and 1/4 wave
on others. Look for resonaces in and around the RV. The o'l grid dip
will help you find them. The grounding braid is suspect.
so are resonaces that include the screwdriver matching coil.
K6EXO
----- Original Message -----
From: Press Jones <n8ug@juno.com>
To: <towertalk@contesting.com>; <w9dni@juno.com>; <n8ug@juno.com>
Sent: Thursday, September 23, 1999 2:08 PM
Subject: [TowerTalk] Squirrely Screwdriver
>
> Looking for ideas to explain strange behavior of a DK3 - one of the real
> McCoy (Don Johnson's) for a close friend(Steve).
>
> This unit is mounted on the rear of an RV to a small platform on a welded
> 1 inch square steel stand at 27 inches above the ground.
> The steel is attached to the chassis and a 1 inch flat braid also runs
> from the antenna base to the RV frame. It can't be much higher or the 80
> meter position would be well over 12 feet.
>
> There are a number of these antennas in the neighborhood in rural
> Illinois mounted on jeeps, cars and trucks, and three of them have the
> same performance characteristics posted here, and all of them, including,
> Steve's, perform well on their owner's vehicle. All of them perform in
> concert with the weird data supplied here when mounted on Steve's
> vehicle, which is a "Trek" RV - rear engine diesel.
>
> Below are two sets of figures which represent mean data from several
> other SD's on their respective vehicles, and the data from all of them on
> Steve's RV. The data are inches of exposed coil above the wipers for SWR
> less than 1.5:1
>
> Frequency others Steve's
> 28.332 0 6 3/4 "
> 24.950 1/4 " 8 "
> 21.350 5/8 " 9 7/8 "
> 18.150 7/8 " 12 1/4 "
> 14.250 1 3//8 " 7/8 "
> 7.250 4 3/8 " 3 7/8 "
> 3.950 12 3/4 " 12 "
>
> No mistakes in recording here - this is the way they read - time after
> time.
>
> The only clear conclusion is that the SD's are all OK, but the RV is not,
> since all perform basically the same in the same spot.
>
> Any thoughts from the SD community as to things we might try?
>
> Thanks,
> (Please note that I will be on the hamfest trail for the next 5 days, so
> our thanks for your kind remarks will not appear until Wednesday next)
> 73,
> Press Jones, N8UG, The Wireman, Inc.
> Certified Quality in product and service for 22 years
> Orders(800)727-9473 or orders@thewireman.com
> Tech help 864-895-4195 or n8ug@thewireman.com
> Check The Wireline for super specials at www.thewireman.com
>
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>
>
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