In message <v01550100b10858b411c4@[207.90.121.52]>, Paul Hrivnak
<palstar@erinet.com> writes
>>>In message <2.2.32.19980209135310.0068155c@pop3.liii.com>, Len Schaier
>>><schaier@avotec.com> writes
>>>I want to build a 300 ohm, 2kw, non-inductive resistor to use as a
>>>dummy load or antenna terminating resistor at about 4 mhz.
(snip)
> Those flanged mounted resistors are poor for return loss and would
>be unacceptable for what G8GSQ has described.The ideal way is to use
>non-inductive carborundum that are high flashpoint oil immersible (Shell
>Diala only). This enables the resistor to dissapate up to 5 times its
>steady state air wattage rating.For the kind of power you will be using
>this is one of the few alternatives. The tin gallon cans are about $6 new
>and the resistors 1" x 6" are about $15 each.The special oil as mentioned
>is available from an authorized Shell distributor in your state. Regards
>Paul
I think we are thinking of different sorts of resistor - the ones I mean
are 'microwave' stripline types. The 800W 50 ohm termination is
specified for 100s MHz and the frequency spec. goes higher as the power
rating reduces. Short duration peak rating is much higher than the cw
value.
A while ago I think I remember an article in the RSGB mag. suggesting
the use of graphite pencil leads (baked to leave pure carbon) in
distilled water dielectric for high dissipation. I wasn't sure if it was
serious - any comments?
Steve G8GSQ
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