Mic mod | uSDX+ | 8 Band SDR | SSB/CW QRP HAM Transceiver | Issue with Iambic paddle + MIC resolved

Problem description:
1) CW iambic mode works well when the Speaker-Mic plug remains disconnected.
2) To switch over to SSB, the mode has to be first changed to LSB/USB, before plugging-in the Speaker-Mic.
3) If the Speaker-Mic plug is plugged-in with iambic mode selected, the rig goes into continuous DIT transmission, and then hangs with TX keyed continuously.
Solution:
This video describes the mod/work-around - to enable trouble-free switching between CW iambic and SSB modes without the need to pull-out or plug-in any connector.
Its's a two-step mod.
The first mod is on the main uSDX+ board, and the second mod is on the supplied speaker-mic (that has an LED to indicate TX). If you are supplied with a different speaker/mic, then the second mod may not be necessary.
#arduino
#wb2cba
#software defined radio
#DL2MAN
uSDR uSDX+ Plus V2 Review 10/15/17/20/30/40/60/80m 8 Band SDR All Mode HF SSB QRP Transceiver + 4000mAh Battery

[@py2bnd-sota411]

When You remove the resistor on the mike you do not only resolve the Dit and Daah problem. You also improve the biasing of the elekret audio sensor since the led is robbing a part of the elekret biasing current. Well done guy👍👍

[@PremMenon]

Yes. Thank you Wolfram! 73, de va3uma.

[@adventureswithsteve2981]

Save all the hassle , just remove the mic when using CW like it was probably designed for

[@PremMenon]

Steven, that's a good idea 😃. Thanks for checking out my video. It's nice to have everything plugged in regardless of the mode. My main reason: the connectors (sockets) do not "look" reliable.

[@dannywhittle4245]

I have a problem with the audio reports using ssb with this radio. The reports I get are distorted audio and possible RF on the signal. Would appreciate any help on this please. Thanks

[@PremMenon]

First off, thanks for checking out the video. To begin with, this rig just has a so-so SSB. I'd isolate the complete final amp stage, connect the pre amp stage output to a piece of wire, tx ssb, monitor your own tx on another Rx in your shack. See if you can resolve ssb without any artifacts/distortion. We can take it forward from there - depending on the outcome. This is just to minimize the unknowns. Let me know. It has been a while since I worked on this rig, but I can hook it back, and compare with the schematic for an in-depth debug. Good luck. 73.

[@dannywhittle4245]

@@PremMenon thanks mate I'm going to first try and put a variable resistor on a studio mic and see if that helps. I will try to monitor with a rtl sdr for monitoring. If no joy in that then I'll try a preamp with volume control. Was thinking the resistor you was on about may have been the problem but I'll have a play and let you know 👍👍👍

[@dannywhittle4245]

@@PremMenon OK my friend I have tried another condenser mic in the front connection of the radio with a variable resistor in line and it makes no difference what so ever and is still distorted :( really have no idea why. The only thing I can think of is have I overdriven the input when using FT8. I came streight off the soundcard into the front of the radio. I've since found out I should have put a resistor in line both on the input and output. Can you shed any light on my problem please. Dan 🙏👍

[@PremMenon]

@@dannywhittle4245 that's very unfortunate, Dan. Again, depends on what test equipment you have on hand. Left to me, I'd do what I mentioned in my first reply. Also, I'd feed a known AF signal (Sine wave) using a known good mic, and monitor the output at every stage. Being the holiday season we are QSYing out to the Grand Canyon shortly; back after new year 1st, therefore not in a position to hook up the rig for any real time debug work.

[@robc3863]

So does this mod improve tx audio quality?

[@ColinMurrayNZ]

i dont suppose you have the circuit diagram for these radios?

[@PremMenon]

I had it, but it's been a while.... You can ask the vendor. They normally send it.

[@ColinMurrayNZ]

@@PremMenon yeah ive been waiting for awhile for a reply, i had some pads pull up from the CAT port trying to find other points to connect it to

[@PremMenon]

@@ColinMurrayNZ Oh! That's too bad. If you Google you should find it. I don't want to make promises I may not be able to keep. I've moved ahead to (many) other projects therefore can't guarantee the schematic availability. Besides, each vendor has something different - although the same concept.

[@srakita]

I have problem with very bad reception from 15m up to 10m...dont know where to sorce a problem. Also self oscillations in speaker or head phones when increase volume on these bands. Any suggestions ? Software version is R103w. 73 de YT7AB

[@PremMenon]

Can you please capture both the issues in a quick video and post it on KZbin? A picture/video is worth a 1000 words. I'll see if I can identify what the problem is after watching and listening to the audio. 73, de VA3UMA

[@srakita]

@@PremMenon thanks for prompt reply. Will post video on YT in the morning since it is 01:30am local but i am still searching for receiver solution.on 40m band have made qso up to 10.000km ...to Japan,Usa,Saudi Arabia..so i am pleased with reception and performamces on 40 and 20m..did not managed to do anything on 15 and up. Running EFHW antena ..

[@PremMenon]

@@srakita QSL. Please send me the link. Good night.

[@srakita]

@@PremMenon kzbin.info/www/bejne/oovGaIprZdd2i9U Here is a small video,but i am not sure will you be able to hear difference in audio level...it is to low from 15m up and when i increase volume there is micropfonia present ...sorry for late reply

Will changing the resistor improve the SSB TX quality?

[@PremMenon]

There's still much to be desired. SSB is not good in this rig. Our communication is understood, but still not good quality. Not worth attempting any further SSB improvement on this rig. Good for CW. Thanks for checking out the video.

[@robc3863]

So reducing the resistor vale to 5k is to boost the low audio from the mike?

[@haramanggapuja]

So you disconnected the LED because you didn't need the light? ;-) The same here on the little box that I have. Since the CW keyer line in this one (and I suspect on the one you have) is shared in the mic jack, I have to wonder if the LED is all that necessary. . . . At the same time, what is your impression of the SSB quality? Listening to the output on the other radios in the shack here, I have to say that it leaves much to be desired. Barely intelligible at all to my mind. I've tried listening on remote SDRs online but my signals too weak to get noticed. 73 de W8IJN

[@PremMenon]

Nils, along with that Mic LED, one more change required...on the main board. My video has the info. You hit the nail on the head! Frankly, the rig is a good example in an academic setting to show/teach the students good coding techniques. Period. Oh, yes, for CW it's okay. SSB? No way. Any changes or upgrades we do is diminishing returns. Not worth. Essentially, the rig overall is a compromise. I believe the uBITx to be a better allround rig. Not SDR. Simple straightforward "superhet" old school technology.....and 100% reliable.... whether in a park or on a mountain! 73. De VA3UMA

[@haramanggapuja]

@@PremMenon In truth Ithink you are absolutely correct: as a direct conversion radio, it's ok but it will never beat a good clean superhet design. Thus I put this and its relatives down as toy radios. Good enough for play but not for serious design or use considerations. 73 de W8IJN

[@haramanggapuja]

Just caught the mic resistor part. Took me a bit to connect my own meandering dots. Pretty sure the non-battery tiny version I have has the same design “flaw.” There are a couple such changes I’d made on my previously owned brick. That’n, well, it’s “special.” ;-). Fun part of these radios - once I get past essential tremor slowin’ me down - is we can mess with ‘em and not blow up too expensive a box. 73 de W8IJN

[@PremMenon]

@@haramanggapuja 😀Nils, talking of Tremors.....I hope you get the strength to overcome that. I know how it is. Work stress related - I went through that....had to stop all my electronic repair work.... couldn't even play the guitar or keyboard....but, that's now put behind me. Tremors gone 👍... 73, De VA3UMA

[@robc3863]

@@haramanggapuja reading the design papers the Tayloe quadrature sampling mixer gives a 3db gain without noise, so it seems it could equal a superhet. My tests against an SGS-2020 show it's pretty close which is amazing for the cost

[@pilotsvvv]

Mars mod for this ...

[@PremMenon]

Thanks for your feedback. No, nothing planned. I've moved on to other projects.