Re: 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.
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-------- Original message --------
From: "WZab - SP5DAA via groups.io" <wzab01@...>
Date: 4/12/25 11:39 AM (GMT-05:00)
To: BITX20@groups.io
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?
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
On Sun, Apr 13, 2025 at 03:17 PM, Gordon Gibby KX4Z wrote:
Yes, it’s still missing dits.
And, less frequently, dahs.
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Re: sBitx v3 - next final MOSFET killed
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
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Re: is it possible to build zBitx firmware on Mac OS x?
thanks Ron..i have plenty of RPi zero's but wanted to use my M1 mac because its a lot faster..;-) ?i'll just use the RPi..
Mark
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Re: sBitx v3 - next final MOSFET killed
Hi Gyula,
?
I have a V2 and run it on lower watts output.
I am curious as to what your "small modifications" were.
?
Thanks
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George VY1GP
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
Yes, it’s still missing dits. ?The full experience of detecting key closure and going all the way to transmit is not happening often enough per second. ? That would drive me nuts.
It seems that Eric demonstrated that the fix proposed works. I’m not clear why it’s not being used. (there may be some other factor that I’m not understanding) ?It is what I have going on all of my V2 units, and it’s a lot of fun!! I think the problem with return to receive is AGC. Perhaps it is being altered during transmit?
Gordon kx4z?
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On Apr 13, 2025, at 16:09, John AE5X via groups.io <ae5x@...> wrote:
? Here is a video with the latest fw installed in the zBitx. CW keying is improved but still poor. Note also the delay in returning to rx after transmitting:
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73,
John AE5X
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
Here is a video with the latest fw installed in the zBitx. CW keying is improved but still poor. Note also the delay in returning to rx after transmitting:
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73,
John AE5X
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Same on CW:
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73,
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John AE5X
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Re: is it possible to build zBitx firmware on Mac OS x?
Depends on what Mac you have and whether the zBitx is running a 32-bit or 64-bit Linux.
For 64-bit Pi OS, you can run an arm64 Linux VM on an M1 Mac, and use that as a build server.
For 32-bit armv7 Pi OS, I recommend getting another Pi, installing a 32-bit OS on it, ssh to it from the Mac, and use that Pi as a 32-bit build server for the Mac.
73, Ron, n6ywu
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On 4/13/2025 11:04, Doug W via groups.io wrote: Courtesy of archive.org, these might help.
index.php/2017/11/23/wiring-up-the-bitx40/ < web/20230321095920/ wiring-up-the-bitx40/>
index.php/2017/11/23/bitx40-circuit-description/ < web.archive.org/web/20220119131525/ index.php/2017/11/23/bitx40-circuit-description/>
Some of the wiring mods may be for PE1NWL amazing firmware.
_._,_._,_ Looks like the original builder started but didn't finish the CW mods. I went through and finished all the necessary mods to get the radio to work in CW. I installed a key jack and decided to just use an external keyer with the radio, since I can't seem to figure out where to change the CW speed in the menu. It is now working on CW, but it still has the quirk that the semi-QSK has to be turned on in order to activate CW xmit. This does, however, prevent me from changing the mode from CW-L or CW-U to LSB. However, I did learn just now that keying up the microphone makes the radio switch into LSB mode. Then keying the keyer automatically switches it into CW mode. Still working out all the quirks of this radio. But at least now I can get on CW with it. -- Tom Sevart N2UHC -- This email has been checked for viruses by Avast antivirus software. www.avast.com
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Re: Can we someday have change logs for the zBitX firmware and screen updates?
Yeah, what I know about git can be painlessly engraved on my left thumb nail in 36 point type. In italic!
-=-=-=-=-=-=-=-=- 73, Gwen, NG3P
Changelogs should be "trivially" available through the git web interface. That doesn't mean that I personally know where the git repository is or how to display the changelogs. I even bet that certain commits could automatically send a change summary to this list.
--
ww6x
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I am currently running 3.021.
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Courtesy of archive.org, these might help.
?
?
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Some of the wiring mods may be for PE1NWL amazing firmware.
?
https://github.com/amunters/bitx40
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OK, I made a little bit of headway. I learned that holding the menu button down makes it go into a settings routine where I was able to change some of the parameters. I didn't know how to get into the settings or if they were available until now.
I turned on the CW capacitive paddles, and just touching the two unconnected wires I was able to make the radio go into xmit mode, but it was not sending any CW and there was no side tone. Looks like I need to connect pin 15 of connector D3 to C107 through a 4.7k resistor. Apparently whoever built this didn't care to use CW.
I also quickly learned that by turning the semi-QSK on, the radio will not switch back into SSB mode until that's turned back off. But without the semi-QSK turned on, it won't go into xmit in CW mode. Not sure if this will be fixed when I make the connection, but at least it's a step in the right direction.
--
Tom Sevart N2UHC
--
This email has been checked for viruses by Avast antivirus software.
www.avast.com
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Re: Can we someday have change logs for the zBitX firmware and screen updates?
Changelogs should be "trivially" available through the git web interface. That doesn't mean that I personally know where the git repository is or how to display the changelogs. I even bet that certain commits could automatically send a change summary to this list.
--
ww6x
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On 4/13/2025 04:25, Vic WA4THR via groups.io wrote: If you have the option to select CW, the radio may have been updated with Munter's fantastic BitX40 software. The attached manual shows the hardware mods needed to operate CW.
=VIc=
_._,_._,_ OK, that may explain what this mess of components soldered together with a couple of unconnected wires is (photo attached). I've circled the bundle, which looks like a couple of caps and resistors, connected to the A1 dit pin. Now I'm wondering if the unconnected wires are for the dit & dah sides of a paddle. -- Tom Sevart N2UHC -- This email has been checked for viruses by Avast antivirus software. www.avast.com
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is it possible to build zBitx firmware on Mac OS x?
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
You could just tell us in two lines of text what you found and put in a bug report on Github? ?It might be less stressful all around. ?
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Re: Fixed: cw latency and wsjtx/flidigi sidetone
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HA3HZ
Gwen Patton
Robert Fairbairn
Jens/HB9JOI