On Sep 22, 2004, at 3:53 PM, Robin Szemeti wrote:
On Saturday 14 August 2004 17:01, Dr. David Kirkby wrote:
Do you have access to a large drum of coax, just capable of taking the
power? Then a long length of it would become lossy and so dissipate
the heat along its length. If you unwound it, it will do it. Don't
leave it wound up, as it will obviously overheat.
I used to use a 500' real of RG/58 coax as my dummy load on 2m with a
pair of 4CX250Bs. That could melt after several minutes, so was a bit
too thin. But 50 feet would have been fine I am sure - the loss was so
high.
hmmm ... just remember a pair of 4cx250s puts out at best 700w on 2m,
this is
a 20KW device ... a 3CX15000 ... think about the dissipation, in a
lossy
line it will be exponential .... so if 100m had say a 10db loss you'd
lose
roughly half the power in 30m, that 10kw in 30m ... or 300w per metre
... I'd
think its life could be measured in seconds ... apart from that, RG8
would
probably not even stand the voltages from 20Kw into 50R,
It will - provided good connectors are used. If the coax is on a roll,
dunk it in a trash-can filled with water.
so maybe a couple
of dozen kilometres of LDF550 might do the trick?
I think I'll continue the search for a load ... I now have a water
chiller
capable of handling up to 45kw, so a water cooled load is looking like
an
option :)
--
Robin Szemeti
Redpoint Consulting Limited
Real Solutions For A Virtual World
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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