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uBitxV6 -by transmitting resets-
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Hello everyone here,
I have been using my uBitx V6 exclusively in CW mode for quite some time now. Recently, a what seems to be "auto reset" occurs during transmission the set then goes down completely and then starts up again happily. I have been searching like crazy for the past few months but I cannot? find the cause.I In the meantime, I have disabled the auto reset of the raduino, but that does not help either.
In the meantime, I do not know anymore, perhaps someone here has an idea? I would be very grateful ?
best 73es pieter (oe6paf) |
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Hi Pieter,
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In addition to Ragav's suggestion, I suggest checking your antenna and connections.? Something may have changed, causing RF to return to the radio.? You can also try putting a common mode choke on the antenna feed to the radio.? Shack RF has been known to cause problems with the uBiTx radio series.
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One way to determine if it is shack RF is to try transmitting into a dummy load.? If reflected RF is causing the problem, the radio should not be reset.
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Another possibility is that the power supply is dropping out. When transmitting, measure the voltage on the radio.
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73
Evan
AC9TU |
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Hello Ragav
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Thanks for thinking along,
I have already applied the solution you propose. In the past, the complaint about the bitx was that the 7805 got very hot.? That was also the reason that I had already removed it from the print and provided it with a large heat sink.
?And to counteract the thundering of the output voltage, I had added an extra 4500uF electrolytic capacitor
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Another thing; I am very new on groups.io and I can't find the answer button here or is there no?
opportunity for an ongoing topic on the groups? maybe you can help me on my way?
Thanks again for your help and thinking along
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best 73es pieter.
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Hello Evan ;
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Thanks for thinking along, what you suggest I have already done in the past, the antenna here is a 2x20m dipole and tuned 1:1 with the s-matsch I a symetric line.?
In the shack there is almost no HF to be detected (some is always present) I also removed the 7805, which gets very hot, from the Raduino print and provided it?
with a large heat sink and added an extra 4500uF capacitor at the output, but all without result, It is driving me crazy, hi
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Thanks again best 73es pieter oe6paf
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Hello you All
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After months of searching, this problem has been solved
Bob, (WB8BEL), came up with the idea to bring the supply voltage from 13.8v to below 12v. Three diodes of the type 1N4007 in series were enough to push this to 11.6v. I then signaled a whole page of the newspaper in cw over the dummy load. In the past, the set (uBitx V6) would definitely go brake down and now it works without any problems. It looks like Bob's idea has turned out to be a golden tip! I would like to thank all the thinkers for their input, Hpe quagn? on freqs
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Tks Agn and Best 73es pieter (OE6PAF) |
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Hello Evan,
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Hello Evan
at the moment I have the diodes in the power line and it works very well at the moment. But your idea also deserves to be tried and easily applied here, I will try this tomorrow, perhaps this is even better because I suspect the raduino of having the error somewhere here, you will hear.
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Thanks so far? ? 73es pieter oe6paf |
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Ted Spencer
开云体育Another possibility is to replace the 7805 with a small switching regulator (around, in my case, an MC34063, but there are better candidates) which remains cool, and significantly reduces the overall supply current.Ted VA3YWA
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Good morning everyone
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Evan's proposal was very tempting, after all, you then retain
the full line voltage of 13.8v available for the output stage. So I soldered two 1N4007 diodes in the positive lead of the 7805. And of course removed the three diodes in the power supply line. However, without result, in an attempt to signal the page of the local newspaper about the dummy load, it went back to the old situation after a minute, The set broke down and immediately restarted completely automatically. The old complaint! I repaired the three diodes in the power supply line and tested the case again by means of a long CW broadcast over the dummy load. The set now behaves very nicely again and the complaint does not return. This fault was very annoying, sometimes it didn't come back for weeks and other times it did three times a day, it was driving me crazy! I searched for months for the solution, who would think about placing three diodes in the power line? Bob WB8BEL so, The HAM community is I think, very special, with my long search for the solution I finally ended up here on this site and then something starts; to come from all corners of the world with ideas and solutions, very special actually. My uBix set is now finally working properly, thanks to the thinkers, I would like to thank everyone again for their input and I hope to meet you in the future when the condx are good, in cw on the qrp bands! ?
Until then,,,,,
Best 73es pieter OE6PAF
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Hi Pieter,
I have been following along, and I even wrote draft reply but did not send.? IMO, you are further along on the diagnostic of the problem and may not truly be at a best solution. ?Since not stated, I infer that your not monitoring supply current and voltage at the uBITX nor RF power out.??Is your power supply up to the task?? Not just for what it was once rated.? Dropping input from 13.8V to 11.6V via 3 diodes reduces the current demand, changes transistor biasing.
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On the digital side, nothing that I am aware, will draw more power in TX than in RX while spinning the encoder to change frequencies.? ?To diagnose the reset, you need to capture voltage levels and reset signal.? Easiest with a digital scope triggering on a level dip of supply domains: (13.8V/12V-in, 5V, 3.3V) and the reset pin on the Nano / DTR from the CH340.??
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Just a few ponderings on my end with the goal of fostering other ideas and you reaching your best solution.?
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Regards,
Gary |
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I agree with Gary that something is causing a voltage drop or a power issue at the 13.8 volts.? CW uses another output for the sidetone and unbalances the first mixer to allow the Si5351 frequency to go to Q90.? Though small, a slight uptake in power is required.? The symptoms suggest a possible thermal shutdown of the LM7805.? You can check to see if it is getting excessively hot (you can not hold your finger on it).
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In addition to monitoring the power supply, also try different bands.
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There is another LM78xx regulator (U2) for the IRF510 bias that is off until transmitting.? If that regulator is the issue, it should not matter whether the transmitter is in CW or SSB mode.
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You could also try one or two diodes to see if that makes a difference.? A variable bench power supply would be ideal.
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You can always accept that the radio must have 12 volts or less.
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73
Evan
AC9TU |
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Ted Spencer
Quite correct! Long continuous CW should impose no great burden on the Raduino, but the average RF power will certainly be higher than sideband work.
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Show quoted text
I had not seen the thing dying: my equilibrium was upset solely by the temperature of the 7805, and I suspect (but did not bother rigorously verifying) that the (high current) culprit was the display backlight. A hot regulator is not a beautiful thing. Cooling the regulator by moving some of its dissipation to several hot diodes is an inelegant solution. I’ve not noticed heat in the 78L05 that biases the output FETs: it provides about 1 mA regardless of RF power. Ted VA3YWA On Feb 12, 2025, at 9:09?AM, Gary Anderson via groups.io <gary.ag5tx@...> wrote: |
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?Hello Gary,Evan,Ted,
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I understand your doubts,
As for the power supply,:? this has been working for years and was once built by myself a large 24v transformer, a thick diode bridge of 80 A, via an lm200 to 13.8v with 4x 4N3771 parallel and a fist full of Elco`s, very basic. When using my KWD 140S 100w SSB/CW, the power supply does not flinch I once tested with the DMM. So that power supply is really not bothered by a qrp set, My knowledge of current digital equipment is somewhat comparable to that of the Stone Age! I recently successfully built the QMX+ from QRP-labs, but what I have been doing now, even if you beat me to death I do not know. The only thing about this thing that I still understand a little is the lpf, the rest of the schematic is also a mystery to me, and that's how I have to look at the raduino. Gary states the following: To diagnose the reset, you need to capture voltage levels and reset signal. ? Easiest with a digital scope triggering on a level dip of supply domains:? (13.8V/12V-in, 5V, 3.3V) and the reset pin on the Nano / DTR from the CH340. ? I understand that, but you have to have those things at home, Of course I also ask the question "how it is possible that three diodes in the power line solve the problem"? and I don't get any further than blaming the raduino and that
is a digital story and then this young man drops out. Don't get me wrong people, I really appreciate your interest but I can't go into too much detail about the digital issues in this
one, it works great now and I just successfully made a qrp connection with sweden and I can finally sleep well again, hi
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Tnks agn es Best 73es pieter oe6paf
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Ted Spencer
开云体育As we so often say: “Nothing succeeds like success.”.?It’s working, Therefore it’s not broken. Therefore you don’t need to fix it. Perfect. Ted VA3YWA
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Hi Pieter,
I believe Your trouble comes from capacitor modification at the output of LM7805.
Transients on power supply rail are occurring during TX/RX switching.
As You wrote - You have swapped electrolytic capacitor with 4500uF - as I understand at the output of LM7805.
This cap is too large for this linear regulator and is not reducing heat of LM7805. At higher frequencies this cap has already high impedance and not filters peaks/transients enough - it's passing them into 5V rail (causing arduino reset). Please add additional 100nF capacitor at output of LM7805 or better replace 4500uF with 10uF and obligatory add mandatory 100nF capacitor or return to single original (was it 1uF?).
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Regards
Tomasz
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