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Help with troubleshooting Bitx40 - no transmit.
#bitx40help
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Neris Biciunas
There are many things that I don't know, and I sincerely thank all of you for the resource that is growing here in this group.
I am looking for some assistance troubleshooting a Bitx40. Go easy on me, I have very little idea of what I am doing. Let me tell you what I do know... -This is my first HF radio, and my first kit build radio - what could possibly go wrong, right? -I am running this radio from a 12v Battery. (12.4v -13.2v ish) -100' of coax to an inverted V that has been tuned to the middle of the band. -Receive works well.? I can regularly hear folks from the western half of North America, and frequently the east coast as well as others speaking Spanish (Mexico?? South America?) -Transmit appears to not work.? I have not made any successful QSO's. -I have a QRP dummy load (), and the voltage measured (between ground and VRMS pin is something like 0.57) (RF power = (0.57^2)/50= .0065 watts) when the mic is keyed. -I have tested the voltages of all of the transistors and while not exactly the same, they are very close to the values published by?Randy, K7AGE -I never saw the "Magic smoke" -There are very few mods to this BitX40.? Allard's code, extra heat-sink one the raduino, and larger heat-sink on the board, extra capacitor on tuning pot, (there is one other capacitor that I added, but at the moment, I cannot precisely describe where I put it), external speaker/mic by BTech -I don't have access to test equipment beyond a multi meter, small dummy load, and an antenna analyser. -I have tried to measure Amps drawn, but I was likely doing something incorrectly as the values were not even close tho what is described in the BitX40 write up. -Nothing gets hot when powered on, no visually obvious defects. -I have listened (via WebSDR) to a frequency that I was transmitting on, and received nothing.? I'm not sure if I was too far away, or if I was really not transmitting.? I live far away from most everything so popping over to the next ham meeting is non-trivial. So what can I test?? Are there any other troubleshooting guides out there? Thanks for any ideas or suggestions that you might have. WA7NJB |
¿ªÔÆÌåÓýWhat were the numbers you got when measuring current? On 10/24/2017 05:41 PM, Neris Biciunas
wrote:
There are many things that I don't know, and I sincerely thank all of you for the resource that is growing here in this group. |
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You're probably very close to a working rig.
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If all you are doing is pressing the PTT button, you won't see any RF going out. On a single sideband rig, you only get RF to the antenna wen there is audio into the microphone. If you don't trust your wattmeter, maybe put a 1 watt 50 ohm resistor (or 4 1/4 watt 200 ohm resistors, etc) on the antenna jack, see if they get hot when attempting to transmit. ?If transmitting 5 watts into a 1 watt resistor, don't transmit for more than a few seconds or you will cook the resistor. Be very careful as you mess around, take a break when you get tired. Put tape over the ends of all the extra leads coming out of that Raduino, don't want them to brush against anything they should not, such as the IRF510 heatsink. If the IRF510 heatsink is not electrically isolated from the IRF510 tab, don't short anything to that heatsink as it is at 12vdc. Make sure your antenna connector is wired up properly. Don't laugh, it happens. On receive, it should be on the order of 150ma (I don't remember exactly) for main bitx40 plus Raduino. With ptt pressed and no audio, it will go up a bit from there, Should see about 100 ma (within 20%) ?into the IRF510 drain (connector PA-PWR1) when ptt is pressed. If it is more than 100ma into the IRF510 with no audio into the mike, stop quickly before it smokes. If it is less, measure the dc voltage at the IRF510 gate when pressing ptt, and tell us the current into the irf510 and the voltage at the gate. Be careful if you choose adjust the 10k pot at rv1 as in the wireup instructions, it is very touchy and if you turn it up too hi the irf510 will smoke. What's worse, it's wired up backwards, so turning it counter-clockwise will increase the bias into the irf510. Safest thing is to remove power from PA-PWR1 and monitor the voltage at the IRF510 gate while fiddling with rv1 to get a feel for how it works. ?The 100ma point will be at around 3 or 4 volts, the smoking IRF510 point will be maybe 0.5v above that. Then adjust that bias back down to zero volts, connect back up PA-PWR1 to a 12v source with a 2 amp fuse, and slowly turn rv1 back up? (counterclockwise!) till get get to that magic 100ma spot. On Tue, Oct 24, 2017 at 02:41 pm, Neris Biciunas wrote:
-I have a QRP dummy load (), and the voltage measured (between ground and VRMS pin is something like 0.57) (RF power = (0.57^2)/50= .0065 watts) when the mic is keyed. |
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Neris Biciunas
OK. ?So a few more facts for the puzzle.
-One of the extra capacitors is 100 pF in parallel with L7. ?As per Wayne NB6M as written up in BitX Hacks Blog. -I tried to measure mA again, and something is really odd. First, I am running power from a battery box, 12.85v. ? All connections are Powerpoles. ?I checked the power at the power distribution block (inside the radio, behind the fuse) 12.90v. ?My multimeter is a Mastech MS8264. ?Black lead is plugged into "COM", red lead into "mA". ?The dial is set to 10 A ?DC. ?The value that I see is -1.10 A, rising slowly to -0.45 A. ?Yes, I said negative values, ?No, I don't have my wires crossed. ?What the heck! Jerry, Thanks for all of the good leads. ?It will take me bit to figure out some of them. ?A few I can respond to now. "If all you are doing is pressing the PTT button, you won't see any RF going out. On a single sideband rig, you only get RF to the antenna wen there is audio into the microphone." ? ? ? Yep, I have tried "hallooooing" into the mic - not apparent effect. "Put tape over the ends of all the extra leads coming out of that Raduino" ? ? ?My leads are pretty tidy. ?Not promising that I did't already short something, but I usually keep things pretty tidy. "Make sure your antenna connector is wired up properly. Don't laugh, it happens." ? ? ?Well, I have replaced the separate leads as supplied by HFSigs, with a short piece of tiny coax to a BNC. ?I am using the supplied connector. ?How do I confirm that POS and GRND are connected to the proper side of the connector (board)? It will take me a bit to figure out the rest of your feedback. ?Thank you very much!? |
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David? WA7NJB If you can add an RF detector probe to your test equipment inventory it might be very useful for measuring RF levels at various points in the transceiver.? There are kits for RF detector probes but they are so simple that you can easily build your own from on-line articles and schematics.? To maximize the value of an RF detector probe you do need to understand how it works and what it is trying to tell you.? Arv? K7HKL _._ On Tue, Oct 24, 2017 at 3:41 PM, Neris Biciunas <nbiciunas@...> wrote: There are many things that I don't know, and I sincerely thank all of you for the resource that is growing here in this group. |
¿ªÔÆÌåÓýIf your meter is set to 10A shouldn't you be plugging the leads in to COM and 10A?On 10/24/2017 09:11 PM, Neris Biciunas
wrote:
OK. ?So a few more facts for the puzzle. |
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Here's Wayne's 100pf hack: ?
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But I think credit for that should go to Don Cantrell: ? Regarding current measurements, if things are strange I suggest backing off to something simpler. Perhaps practice measuring the current through a 100 ohm resistor from a 9v battery. I assume you are supplying 12v to the PA-PWR1 connector when attempting to transmit. > ?How do I confirm that POS and GRND are connected to the proper side of the connector (board)? With an ohmmeter. ?Make sure board ground is connected to BNC shell. ?Make sure board antenna connection is connected to BNC pin. ?And make sure there is no connection (as seen by the ohmmeter) between the two. Jerry On Tue, Oct 24, 2017 at 06:11 pm, Neris Biciunas wrote:
OK. ?So a few more facts for the puzzle.? |
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Point of basics: the multimeter measures *Voltage* - always! When measuring Current it is measuring the voltage dropped by its internal (small) resistor in series with whatever load you conned.. As such your Red lead (to 10A ) goes to your battery Positive, and the black lead (COM) to the Rig (BitX, the 'load') positive, and it will measure + voltages as above and display them suitably scaled as positive (+) currents.
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Here's an old post on diode RF probes and AC measurements in the Bitx40 power amp:
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? ?/g/BITX20/message/22764 And the bottom paragraph here; ?? ? ?/g/BITX20/message/21941 A few other webpages on rf probes: Stephen wrote: ? > ?If your meter is set to 10A shouldn't you be plugging the leads in to COM and 10A? I think he nailed it. Jerry On Tue, Oct 24, 2017 at 06:30 pm, Arv Evans wrote:
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Amendment: *your* multimeter ... I assumed it to be a modern digital one. The old analog 'originals' measured Current - again, always - a completely different philosophy that relied on the current through the coil of the meter movement to deflect the attached pointer over its scale. The usage of the leads remained the same. 73 de ZL2DEX |
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It's good you posted this information with such a clear photo.
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But I have a thing about giving credit where credit is due, especially if that source can give needed additional details. The back-to-back diode mod comes from Raj: ??/g/BITX20/message/19105 Note that he suggested adding an incandescent lamp, which can be quite effective: /g/BITX20/message/21901 Here's a few more notes about what can blow in that transmitter: /g/BITX20/message/31352 As mentioned previously, I believe Don Cantrell is the source of the 100pf mod to the LPF. His blog post gives considerable detail, including before and after plots: ??? Jerry, KE7ER On Wed, Oct 25, 2017 at 06:31 am, Al Duncan VE3RRD wrote:
Don't forget to add the two 1N4148 protection diodes as shown at . Worthwhile added insurance for your BITX40. |
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Neris Biciunas
Yes, the mic is a Baofeng style handset.? It seems to me that I ended up switching two of the leads from the Miklor diagram to get mine to work as well.? Unfortunately, I do not remember what exactly was switched.? I do know that the speaker works though.
I have tested the PTT function using the PTT switch supplied by HFSigs.? I guess if the mic is not wired correctly, I wouldn't get a response from the switch alone.? I should try the supplied mic as well. |
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Neris Biciunas
Thanks Jerry for correcting my reference for the 100pf mod to the LPF.? I meant no disrespect.? Simple ignorance.
-So I have confirmed that my antenna is wired correctly.? COM to bnc shell, board antenna connected to pin, no continuity between shell and pin. -I was also able to measure mA (thanks to the patient instruction of Dexter N Muir) "... As such your Red lead (to 10A ) goes to your battery Positive, and the black lead (COM) to the Rig (BitX, the 'load') positive, and it will measure + voltages as above and display them suitably scaled as positive (+) currents."
My results:? 12.6v at the battery.? 1.02mA on receive.? 2.30 mA on transmit. -"I assume you are supplying 12v to the PA-PWR1 connector when attempting to transmit." ? ?Yes, that is correct. |
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I'd guess those figures are more like 102ma and 230ma.
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And that you are not be including the Raduino in those figures. You might look over the rest of these links once you've sorted out the above readings. ??/g/BITX20/message/33943 Jerry On Thu, Oct 26, 2017 at 08:09 am, Neris Biciunas wrote: My results:? 12.6v at the battery.? 1.02mA on receive.? 2.30 mA on transmit. |
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Neris Biciunas
Great news!
I have made significant (if not slow) progress towards a functioning radio. I have narrowed down the source of my issue to the handset that I am using.? It is a mic/speaker/PTT combo with a Kenwood style 2.5 and 3.5 set of jacks.? I have checked and triple checked (and even a "peer review") of the wiring as per the Miklor diagram.? When fully wired together, the radio behaves as if the speaker and mic connections are reversed.? For example:? with only the speaker wired, the radio behaves as it should, and I hear static in the speaker (connected to a dummy load).? When I connect the PTT wires, the speaker still functions, and when the PTT switch is pressed, the speaker cuts out, and amps measure appropriately with audio and without.? When I connect the wires for the mic (disconnect the kit supplied mic), the speaker is cut off, and I measure a continuous output voltage on the dummy load (without PTT switch depressed). Questions:? Does anyone have any specific feedback as to a potential error in the wiring diagram by Miklor?? Should I replace the handset mic with the one supplied with the kit? Thanks again for your thoughts |
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Neris Biciunas Some microphones have a set of normally open contacts for activating the PTT circuitry. Others use current drawn by the microphone to trigger current sensing circuitry inside the radio to activate the PTT function.? If using the current sensing circuitry type microphone, it should be possible to build that circuitry into your radio, or maybe inside the microphone itself.? Arv? K7HKL _._ On Wed, Dec 20, 2017 at 2:07 PM, Neris Biciunas <nbiciunas@...> wrote: And one more question: |
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