[Elecraft] OT: heat sinking resistors

[Don Wilhelm]

Phil,

Thanks for that information.  Mine are mounted to a heat-sink culled 
from a CPU cooler, and the connector is mounted to a piece of aluminum 
angle also affixed to the heat sink.  This assembly is standalone and 
does not connect to any other ground plane.  Although the heat sink may 
constitute a small ground plane, the fact that it is isolated may 
account for the difference in the measurement results.

BTW, I have found Caddock to be more consistent than Ohmite.  Caddock 
advertizes their 50 ohm thick film 1% resistors as non-reactive, and the 
last time I looked, Ohmite did not make that statement.

73,
Don W3FPR

Phil & Debbie Salas wrote:
> If they are mounted against a ground-plane (which is often the case for 
> heat-sinking), I've found that the 100-watt resistors are not too good above 
> 50 MHz.  The 30 watt resistors are better, but the 15 watt resistors are 
> best thru 2-meters.  I built a series of 50 ohm terminations where the 
> resistors were bolted to a brass plate, and the brass plate was attached to 
> a N-connector.  The resistor leads were about 0.2" long (one pin attached to 
> the connector center pin, the other soldered to ground).  Measured with an 
> AIM4170 up to 180 MHz.
>
> Phil - AD5X
>   
>