Re: [Amps] 20kw Dummy load?

[R.Measures <r@somis.org>]

On Sep 23, 2004, at 7:58 PM, Michael Tope wrote:

> Has anyone tried submerging MFJ Cantenna's into a water
> tank.

The weakness of such loads is that cooling oil is a lesser conductor of 
heat than water.  The tradeoff with water is that it is so corrosive 
that it can not be left in contact with the R for long periods of time. 
 Thus, coolant water must be added before testing and drained after 
testing.
.
>  I was thinking of building up some power dividers and
> running 4 of those cans in parallel to make a cheap high power
> load. One can will take 1.5KW, but the duty cycle is pretty low
> (something like 1 minute on, 10 minutes off).

Michael -- Have you ever measured the resistance of an MFJ  or Heath  
Cantenna After 1-minute of  NØN (hammer-down)  at 1500W?


> Seems like
> conduction cooling between the can body and a water bath
> would be of some benefit.

In a long test, yes, but the main problem is bubbles forming in the 
cooling oil at the surface of the resistor.
cheers
> Mike, W4EF................................
>
>
> ----- Original Message -----
> From: "DF3KV" <df3kv@aol.com>
> To: "Dr. David Kirkby" <david.kirkby@onetel.net>; 
> <list@redpoint.org.uk>
> Cc: <amps@contesting.com>
> Sent: Thursday, September 23, 2004 4:05 PM
> Subject: Re: [Amps] 20kw Dummy load?
>
>
> > > Well from initially wanting to borrow a large load for a few days
> > over a
> > > month ago, you have now got a water chilller, but sitll no load. I
> > may
> > > well be wrong, but suspect that you could make a suitable load from
> > > lengths of suitable coax.
> >
> > I was using  length of RG141A/U connected to a smaller Bird dummyload,
> > sunk
> > both into a bathtub, works pretty well.
> > Connectors are crimped N, did that with up to 6KW on a 70cm amp, RG141
> > was fed by 7/8" hardline. For HF only longer runs of RG141 are needed
> >
> > 73
> > Peter
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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