On Apr 2, 2006, at 11:52 PM, Steve Thompson wrote:
>
>
> Dan Hearn wrote:
>
>> I don't believe there is room inside the chokes for two 2watt
>> resistors in
>> parallel. I think the 2 parallel 1 watt resistors might run cooler
>> than a
>> single 2 watt job in this spot.
>
> Yes, they might have larger surface area, but they're still carbon comp,
> which is a fundamental flaw. Heat will change their value - not just
> running on 10m, but conducted and radiated heat from the tube. There's
> bags of room for a 3W metal oxide resistor, which will be far more
> trustworthy.
Out of interest, I've just measured the original, then swapped the
resistors for a Dow Corning FP2 22R. I measured up to 200MHz, and the
difference between them is less than the thickness of the trace on the
Smith chart display. I've run FP2s until the markings are no longer
visible, just uniform charred, and the resistance is still within the
spec. of 2%. Try that with carbon comp :-)
Steve
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