Re: sBitx v3 - next final MOSFET killed
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“But the RD product is only guaranteed up to an SWR of 20 to one” ??? Oh… how did you come to that conclusion? ? ? Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ ? Owner - Operator Big Signal Ranch – K9ZC Staunton, Illinois ? Owner – Operator Villa Grand Piton – J68HZ Soufriere, St. Lucia W.I. Rent it: ? Moderator: North American QRO Group at Groups.IO. Moderator: Amateur Radio Builders Group at Groups.IO. ? email:? bill@... ? ?
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From: [email protected] <[email protected]> On Behalf Of Gordon Gibby KX4Z via groups.io
Sent: Sunday, April 13, 2025 7:20 PM
To: [email protected]
Cc: [email protected]
Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed? I can’t claim to be an RF engineer. But the RD product is only guaranteed up to an SWR of 20 to one. ?Looks like it has much lower input C ?so easier to drive. ? However, its drain source voltage limit is 50 V whereas the IRF 510 and IRF 520 ?are 100 V. On RF parts, the Mosfet is going for eight dollars each, so I think you’d be looking at $15 higher price at least. Because there’s two of them. Again, I’m not an RF engineer!!?
On Apr 13, 2025, at 20:15, Michael Bales via groups.io <mikebales73@...> wrote:
? 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.? -------- Original message -------- 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 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)?
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Mike - K8MCB?
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Mike - K8MCB?
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