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Re: [Amps] kw dummy load resistors.

To: Jim Thomson <Jim.thom@telus.net>, "amps@contesting.com >> Amps Amps" <amps@contesting.com>
Subject: Re: [Amps] kw dummy load resistors.
From: Roger <sub1@rogerhalstead.com>
Date: Fri, 19 Feb 2010 08:43:12 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Jim Thomson wrote:
> Date: Thu, 18 Feb 2010 23:08:44 -0700
> From: John Lyles <jtml@losalamos.com>
> Subject: [Amps] kW dummy load resistors
> <snip>
>
> ##  the resistors the other fellow's mentioned on the Mouser site are
> INDUCTIVE, and may well not  work on HF ! 
>   
I thought Mouser listed them as non inductive.  I'll have to look again.
> ## BTW,  I have several old globar TYPE CX  200 ohm/275w resistors
> that are in air cooled loads. They can NOT immersed in oil. They are NOT
> glass bodied types.  Globar tells me the old CX types  were made back in the
> 60's.  Air cooling only, on those things. If in oil, they will absorb oil, and
> resistance will RISE.   Yes, bring money, lots of money.  The palstar
> load is good. Each resistor is 12" long x 2"  diam. Dunno if their resistor's
> can be immersed in oil or not. 
They look and feel exactly like the old glowbar resistors even to the 
greenish, gold ends. They are rather granular and porous, not something 
I'd be comfortable sticking into oil unless it were 200 fluid which is a 
basic silicone fluid that comes in a tremendous range of viscosities 
from about like alcohol (used to treat "dry flies") all the way up to 
something on the order of 6000 centistokes, or nigh onto being close to 
taffy.

However getting enough of the lower viscosity stuff, say a bit thinner 
than 10 weight motor oil  would probably cost more than the entire 
system you are talking about above.
There are two of them in the DL5K I have here, but they must be around 
17 or 18" long as they go from one end of the cabinet to the other.  
They'll take the legal limit continuous with the fans running in high 
gear. Beyond that it's so many seconds on and so many off with the ratio 
varying according to the amount of power dumped into them.
>  Globar does NOT  make a 12" x 2"  diam
> resistor, too bad, only 24" x 2".. and also  18"  x 2" . 
>   
That 18 X 2 may be what Palstar is using. However due to the size they 
probably wouldn't work well beyond HF.  I'll have to measure them to be 
sure about that length.

73

Roger (K8RI)
> http://www.globar.com/ec/bulk-ceramic-resistors/tubular-resistors.html
>
> Later........ Jim  VE7RF
>
>
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