[Amps] 20kw Dummy load?

[R.Measures]

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