James,
From what I have read, it all depends on the kind of thermal compound
that is used. If you rate them in terms of thermal conductivity only,
some are slightly better than the thermal pads and some are worse.
OTOH, if you rate thermal paste in terms of 'messiness', it is far, far
worse than the thermal pads. With thermal paste there are several
variables - how thick a coating?, how much pressure on the mounting
screws? - yes with the thermal pads it is necessary to go back after 10
to 20 hours of operating at high power to snug the mounting screws down
again, but IMHO, that is a small price to pay for the 'neatness' and
repeatability of the thermal pads.
73,
Don W3FPR
James Cutler wrote:
Just a quick note to say that I have built the KPA100 and installed and
aligned it, and it is working fine on all bands. When I built my K2 at
the beginning of the year, it also worked fine, and still is. I have to
say that over all, I am happy with the radio, and it's performance.
I have one query though, I am wondering why Elecraft have opted to use
thermal pads on the PA transistors in the KPA100 as opposed to heat
paste? (A lot of linear amplifiers that I have seen over the years use
thermal paste on the PA transistors without apparent problems.) I just
suspect that the thermal resistance of a thermal transfer pad may be
higher than that of thermal paste......please advise me if I am way off
on this point.
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