The QRPGuys new DSB transceiver requires the 3xBS170 FETs
to have some heat sinking.
Attached is photo of my solution. I used some 7mm wide
heat sink tape that I bought off of ebay for cheap that
came in a 10m or larger length roll. I use it for heat
sinks that come without the tape for CPUs.
Allows heat sinking and allows replacement if ever needed.
I find it much easier than using wire and/or aluminum strips
with screws for hold downs.
I,too, dislike with a passion the use of 3xBS170 FETs for
finals. The first time you transmit without an antenna
connected, have a high SWR or have a short at the BNC or
later, you will blow the finals. I know that Steve Weber
loves to use these puppies because they are so cheap, but
it is such a hassle to replace them. The DSB xcvr as it
is now has no zener protection, but you could easily
solder a zener in place beneath the board.
Ken shows 4W out on 40m. That means a peak voltage of
20V. So I'd recommend a 22V zener or higher at 1W rating
across the PAs. You know the drill.
I think that someone may have mentioned the use of the
2.54mm headers like Diz used in the 5W for use on the
PAs and this will allow replacement without having to
get the soldering iron out.
Some one come up with a replacement transistor. You have
to have done it, none of the 'I think this will work' to
lead us off into the weeds. TIA.
FYI
chuck, k7qo, trouble maker
