Re: heat sink upgrade #parts #bitx40

Doug W

As a follow up to my post about this heat sink, I did some testing of digital Tx'ing into a dummy load yesterday as I think I have my digital interface set up the way I want.  I did not use anything to test the temperature other than touching the MOSFET and heat sink and going by feel.  At a full 7 watts out nothing got more than just barely warm at FT8 cycles running for about 15 minutes.  At WSPR timing both the IRF510 and heat sink got hot enough I was double checking the junk box to make sure I had a few spare IRF510's.  Bottom line, I think this heat sink is ok for occasional FT8 operations at full power (which was all I wanted it for) but if WSPR is your flavor of choice you'll need to crank the power way down.  All in all I got what I wanted for about 73¢.  I should also mention that although it is hard to tell in the picture the MOSFET is fully sitting on the silicone pad.  I lined the pad up with the heat sink overlooking the fact the the IRF510 is angled coming off the board.  Fortunately the pad was wide enough to accommodate my error.

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