Re: Transmitter gain calibration
Mel Farrer, K6KBE <farrermesa@...>
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As a reference on the junction of the RF transistor and the heat sink, I speak from personal manufacturing experience. There are two issues.
First, the flatness of the mating heat sink surface. Flatness can be measured with a micrometer or by using a straightedge and lay down a slick of heat sink compound and look for areas of white, none should be visible.
Second, is the flatness of the transistor base. If one wishes to know if the transistor is seated properly with maximum contact with the heat sink, before soldering it down, one must put a .005 mil slick of heat grease compound on the two hole mounted transistor base plate and finger tighten the screws down, then take the screws out, remove the transistor and look at the morue pattern. If the pattern is spectacled, that is, has a uniform pattern across the surface with lots of metal showing through, the surface tension was adequate for the test. If areas that show white grease that is not compressed, the flatness of the base plate is a problem. Address that problem now. Then when final assembly is made, only go another 1/4 turn----no more. On Stud mounted transistors, the ring around the stud must be uniform in display.
There is a manufacturing MIL spec on this, but memory fails.
I hope this helps a little.