[TowerTalk] TowerTalk Digest, Vol 172, Issue 38

Guy Olinger k2av at contesting.com
Thu Apr 27 13:47:12 EDT 2017

On Thu, Apr 27, 2017 at 10:31 AM, Howard Hoyt <hhoyt at mebtel.net> wrote:
> 1) The horizontal feed point transformer and line isolator are only good to
> several hundred watts CW or SSB despite their claims of 1500 watts.  On CW I
> can see the SWR rise on a long transmit cycle at 500W at certain
> frequencies.

Having disassembled a couple of the Carolina Windom devices that W0UCE
burned up running 1500W CW to them, I can attest to their weakness.
The windings were RG8X wound on what appeared to be adequate ferrite
cores. The RG8X had melted the inner dielectric and allowed the center
conductor to short to the shield. There was some case to be made that
the ferrite rod had heated, but the melt did not seem to begin at the
jacket next to the ferrite rod.

 The device could be easily rewound and refabricated with RG400, which
would remain steady, and is rated to 7 kW.

However, I suspect that the loss in the RG8X was dampening the SWR,
which if left high would be a principal customer complaint. This and
cost would be the obvious reason that RG400 was not used in the first
place for a true 1500 watt version.

The improvement was never tried because Jack moved to a new place and
put up some eclectic OCF's for 40 where the short end went nearly
straight down, mostly parallel to the coax and seemed to work fairly
well, well enough that the subject was closed.

He had an inverted L over an FCP on 160, which was switched into an
end-fed half wave L on 80, which worked very well. And he had a hex
beam for 20 and up.

Redoing the devices with RG400 might do it for someone who has burned
up one of them.

73, Guy K2AV

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