Final PA SWR protection with zener diode?

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thrillscience
 

Posts: 4
Joined: 16 Sep 2022, 15:15
Location: California / Tel Aviv

Final PA SWR protection with zener diode?

Post by thrillscience »

Greetings! I'm on vacation in 9H/Malta and I brought the (tr)uSDX with me. I was able to make a number of contacts on FT8 and CW with an EFHW off the hotel balcony, but somehow I managed to blow out the final transistor. I'm using the "high band" board, which I assembled, and I bought from a DL2Man approved vendor.

I'm not sure how I blew it--I'm using the "QRPGuys" EFHW tuner. The "Watts" setting when I key down in CW, whether or not 12v is connected says "0.01 watts".

When I get back home and can fix it, I was wondering if there's anything I can do to protect the final. I see that some users of similar style QRP rigs use a zener between Drain and Ground. (See https://www.youtube.com/watch?v=7hUmkE84kfA )

Have any of you tried that with the (tr)uSDX, would it be connected the same way, what voltage Zener do I use, etc?

Thanks!
LILO
 

Posts: 69
Joined: 12 Aug 2022, 09:15

Re: Final PA SWR protection with zener diode?

Post by LILO »

thrillscience
 

Posts: 4
Joined: 16 Sep 2022, 15:15
Location: California / Tel Aviv

Re: Final PA SWR protection with zener diode?

Post by thrillscience »

Thanks!

Despite DL2MAN's recommendation against it, I'll build a "travel" RF board with it on. Even if less efficient, it would be nice to have a "protected" one to prevent this from happening again. When operating with a make-shift antenna on a hotel balcony or out a window, a breeze or passerby can knock my SWR up during an FT8 transmission and fry my output, as happened to me on this trip to Malta/9H, and then I'll be off the air without a way to fix it.
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