It's been mentioned before, repeatedly. I agree. I would gladly pay the extra $5 it would cost to go with rd16hhf mosfets. You can have a SOLID 20 watts up into 10m, and not worry about blowing one if you look at it the wrong way.?
toggle quoted message
Show quoted text
-------- Original message --------
From: "Gerald Sherman via groups.io" <ve4gks@...>
Date: 4/13/25 7:50 PM (GMT-05:00)
Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed
I would rather pay a little more for a better output transistor than save a dollar or two on the cost.? Perhaps HFS could take note of this.
Gerry
On 2025-04-13 21:15, Michael Bales via groups.io wrote:
Such is the nature of using MOSFETS not designed for RF amplifiers.? I got so sick of the PA failures with my v3, I built one of K9HZ 20w PA boards and just bypassed the entire PA section of the v3.
-------- Original message --------
Date: 4/12/25 11:39 AM (GMT-05:00)
Subject: [BITX20] sBitx v3 - next final MOSFET killed
Hello,
My sBitx v3 has killed next final MOSFET. Again, as
previously, only one was dead:
However, this time the failure wasn't caused by overheating (the fan was cooling the heatsink and its temperature was ca 30 C) but by SWR.
I was operating my device remotely via WiFi in FT8 mode, and my ATU got crazy. Unfortunately, I could only see the increase of SWR on my laptop, and the connection got broken. I couldn't cease the transmission immediately. When I reached the sBitx, it
already showed the output power 0W.
Well, when replacing them, I have exchanged the mica insulators with AlN ones. Let's see how long is it going to survive now.
BTW. Is it possible to replace IRF510 with other MOSFETs (maybe more expensive, but offering higher maximum voltage and better power at 28 MHz)?
?
73,
Wojtek SP5DAA
--
Mike - K8MCB?
--
Mike - K8MCB?
