On Tue, Aug 22, 2023 at 06:45 PM, Chris KB1NLW wrote:
The flat surface of the BS170 contacts the surface of the PC board.? Being a six layer board this should dissipate heat better than the QDX.? (I do put a little thermal paste on mine to help conduct.)? Hans has explained that the washer on top of the BS170 is to press the BS170s down to make good contact with the board and not primarily to dissipate heat.
I have lost one BS170 on my QMX most likely due to high SWR possibly during? auto antenna tuning or even transmitting without any load - though I don't recall? doing this.? Even with better heat sinking it may not be possible to protect the BS170s from the power reflected into the radio from high SWR.? I believe Hans may build in firmware protection based on the SWR hardware sensing in the QMX
Ah yes - makes sense. Mainly I was worried about IC503, which is over the discharge surface and gets very warm.
