BITX20@groups.io | sBitx v3 - next final MOSFET killed

sBitx v3 - next final MOSFET killed

WZab - SP5DAA All Messages By This Member #117221 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
HA3HZ All Messages By This Member #117223 Wojtek, ? I'm sorry you went this way, but you can learn from your own mistakes. I'm just recommending it, because it worked for me (it's true that I'm not using it in remote mode) that the power supply protects against overcurrent intake with current limitation. Before replacing the FETs, it is advisable to select the new ones with almost the same opening voltage. Bias setting should be done with a maximum 2.00 A power supply. I have v2, which has an IRFZ24N built in, and these are more sensitive to overvoltage and overcurrent. I replaced it once because I tested it on a battery (without current limitation) and I'm still using them. I think this is due to the current limitation. The limitation is 12.5V and 6.50 A. I currently have over 10k connections in 1.5 years and I use one antenna (without antenna tuner) on 3 bands (7-14-21MHz) with a slanted vertically fed delta loop antenna. In short, I am satisfied with the v2 hardware, although I have made several small modifications. Most of them were aimed at reducing the temperature. -- Gyula HA3HZ
George Privett All Messages By This Member #117255 Hi Gyula, ? I have a V2 and run it on lower watts output. I am curious as to what your "small modifications" were. ? Thanks ? George VY1GP
HA3HZ All Messages By This Member #117258 On Sun, Apr 13, 2025 at 10:17 PM, George Privett wrote: I have a V2 and run it on lower watts output. I am curious as to what your "small modifications" were. When I replaced the FETs, I replaced the mica with an AlN (aluminum nitride) ceramic plate 22x28x0.6mm. On the back heatsink I put a quiet fan (92x92x25mm), not fixed, just clamped between two fins. I attached an intermediate bracket to the back of the RPi4, to which I attached a 50x50x10mm fan, also 12V. The fans cool continuously when turned on. I could not finely regulate the Bias circuit, so I found a solution on the F5NPV side: 78M05 and 6 Si diodes that sense the heatsink temperature. Currently, I am using the JJ 64-bit Image v4.4 sBitx. The power supply operates with a current limit of 12.5V 6.5A. If you type my callsign into the search box on the forum page, you can find how I solved the shielding issue that is not mentioned here. That's it in short. -- Gyula HA3HZ
Michael Bales All Messages By This Member #117260 开云体育 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. toggle quoted message Show quoted text -------- Original message -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
K9HZ All Messages By This Member #117270 开云体育 And how is that working out for you? ? ? 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@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Michael Bales via groups.io Sent: Sunday, April 13, 2025 4:15 PM To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
Gerald Sherman All Messages By This Member #117276 开云体育 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: toggle quoted message Show quoted text 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
Michael Bales All Messages By This Member #117279 开云体育 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) To: [email protected] 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
Gordon Gibby KX4Z All Messages By This Member #117281 开云体育 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!!? Gordon kx4z? toggle quoted message Show quoted text 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 -------- From: "Gerald Sherman via groups.io" <ve4gks@...> Date: 4/13/25 7:50 PM (GMT-05:00) To: [email protected] 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] Subject: [BITX20] sBitx v3 - next final MOSFET killed Hello, My sBitx v3 has killed next final MOSFET. Again, as previously, only one was dead: <fet1.jpg> <fet2.jpg> 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?
Michael Bales All Messages By This Member #117282 开云体育 Good, I need to get another 20w kit from you soon. I've been bouncing it between the v3 and my radioberry v2. I eventually found the j7 connection that I missed before, so I could take the signal from there. toggle quoted message Show quoted text -------- Original message -------- From: K9HZ <bill@...> Date: 4/13/25 6:37 PM (GMT-05:00) To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed And how is that working out for you? ? ? 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@... ? ? From: [email protected] <[email protected]> On Behalf Of Michael Bales via groups.io Sent: Sunday, April 13, 2025 4:15 PM To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
K9HZ All Messages By This Member #117290 开云体育 On this subject…. As a person who designs and sells inexpensive electronics… one learns very quickly that your designs must be robust and forgiving… or they break easily and end up relegated to a junk pile.? So, a PA must be able to tolerate mistakes without failing (with an open or shorted antenna), without over-heating, and be inexpensive.? ? ? 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@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Michael Bales via groups.io Sent: Sunday, April 13, 2025 7:15 PM To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? 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 -------- From: "Gerald Sherman via groups.io" <ve4gks@...> Date: 4/13/25 7:50 PM (GMT-05:00) To: [email protected] 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?
K9HZ All Messages By This Member #117291 开云体育 “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@... ? ? toggle quoted message Show quoted text 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!!? ? Gordon kx4z? ? ? ? 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 -------- From: "Gerald Sherman via groups.io" <ve4gks@...> Date: 4/13/25 7:50 PM (GMT-05:00) To: [email protected] 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] Subject: [BITX20] sBitx v3 - next final MOSFET killed ? Hello, My sBitx v3 has killed next final MOSFET. Again, as previously, only one was dead: <fet1.jpg> <fet2.jpg> 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?
K9HZ All Messages By This Member #117292 开云体育 Cool… just let me know.? I have enough parts for about another 300 kits.? I’ve sold more than 1,200 to date. ? ? 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@... ? ? toggle quoted message Show quoted text From: [email protected] <[email protected]> On Behalf Of Michael Bales via groups.io Sent: Sunday, April 13, 2025 7:22 PM To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? Good, I need to get another 20w kit from you soon. I've been bouncing it between the v3 and my radioberry v2. I eventually found the j7 connection that I missed before, so I could take the signal from there. ? ? ? ? ? ? -------- Original message -------- From: K9HZ <bill@...> Date: 4/13/25 6:37 PM (GMT-05:00) To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? And how is that working out for you? ? ? 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@... ? ? From: [email protected] <[email protected]> On Behalf Of Michael Bales via groups.io Sent: Sunday, April 13, 2025 4:15 PM To: [email protected] Subject: Re: [BITX20] sBitx v3 - next final MOSFET killed ? 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 -------- From: "WZab - SP5DAA via groups.io" <wzab01@...> Date: 4/12/25 11:39 AM (GMT-05:00) To: [email protected] 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?

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