(tr)uSDX Forum

Just received a (tr)usdx from one of the recommended AliExpress sellers.

I was wondering about mic gain settings...there doesn't appear to be a way to set mic gain. Or is the tx-drive setting equivalent to mic gain?

I am using with an external mic, on a headset, hence wanting to optimise gain settings.

Thanks

I’m wondering the same. I had a brief 40m SSB QSO with a friend yesterday afternoon and my voice was more or less unintelligible by the other party.

73,

Robert, WA2T

I seem to have the same issue. I was told my audio was distorted. At that point the TX Drive was set to 4.

I changed it to 2 and will test this soon.

I've mainly operated CW and digital modes from my (tr)uSDX's but I've done some testing with SSB, both with the internal mic and a modified Baofeng style mic.

In both cases - for best audio, speak as close as is possible to the microphone - the further away you get, the more distorted to voice signal becomes. I believe Manuel has stated this elsewhere.

I modified the Baofeng mic with a little piece of velcro tape and some fabric, this seems to prevent the worst of the audio popping from being so close to the mic.

SteveL wrote: ↑02 May 2022, 20:35 I seem to have the same issue. I was told my audio was distorted. At that point the TX Drive was set to 4.

I changed it to 2 and will test this soon.

I left mine on the default 4 and have been quoted as having very good audio, I didn't tell him what I was using but I had the same comments from 3 other qso's

With the uBitx some had better luck with a more sensitive element ( more gain built into the element itself, I think )
"Mouser# 665-AOM-5024L-HD-R
Digi-Key# 668-1596-ND
MFG# AOM-5024L-HD-R"
The subsitute's sensitivity says -24 instead of -40 so might not have to yell ( if I understand it right, all seems backwards to me but... )
And it is a 20-20k Hz instead of 100-10k Hz which is probably not better for our purposes.

kinggreene wrote: ↑05 May 2022, 17:49

SteveL wrote: ↑02 May 2022, 20:35 I seem to have the same issue. I was told my audio was distorted. At that point the TX Drive was set to 4.

I changed it to 2 and will test this soon.

I left mine on the default 4 and have been quoted as having very good audio, I didn't tell him what I was using but I had the same comments from 3 other qso's

Thanks for the info @kinggreene.. I'll do a bit more testing.

Thanks for the replies

I have set tx gain to 2, based in listening to my trabsmission on another radio.

The audio tx on seems to be okay with the inbuilt mic, but I would really prefer to hse a fist mic...and with the fist mic the audio is roo quiet.

Really need r be able raise the mic gain...its a great radio but unless I have misunderstood, this seems like a glaring omission

I just managed to get FT8/FT4 working with the (tr)uSDX and am wondering exactly the same:
What is the expected "good modulation" maximum AC voltage level that the transceiver wants to see?
I also have the problem that I speak not very loud and my TX audio is probably very bad.

Falling into my old mis-habit of overthinking things (but not properly) I fiddled with the HW and saw that AREF is 1.1V which would in theory mean 1.1Vpp for using 100% of the ADC input range. Which clearly is something that cannot be true, as the electret capsule will produce less, so there is probably some fixed gain/scaling inside the firmware to amplify the signal. Alas since it is all number crunching inside the ATMEGA, somebody has to tell us what fixed scaling is applied, what the digital HPF/LPF does to that and then how "TX Drive" affects the end result.

At the moment I use ~200mV Vpp from my USB soundcard, but that is just guesswork / try & error...

If we would know the input level the TRX likes to see, adjusting my audio output on the USB soundcard and/or adding a small microphone amplifier / finding a suitable external microphone would be easy.

Edit: This could be over engineering, but i was thinking of maybe adding a small limiter/compressor for the microphone using for example an SSM2167.

-Tobias

I recently got my uSDX. I get the info from my QSO partners, good signal, audio quality with internal microphone very bad, no treble.
What do I need to do, how to improve the audio quality?
73 DM6JKC

Hello OM,

if your signal is good attested by the qso partner and only higher frequencies are missing than everything is okay!
The (tr)uSDX is not a Yaesu, Icom or Kenwood trx, it does his modulation by calculations on a 8-Bit Microcontroller with 20MHz not capable of calculating floating point by itself...
So your audio is super for the capabilities of the Microcontroller
It will never be HiFi not with any other microphone.... just live with the sound and this knowledge.

73 de Chris

Hallo Chris, tnx für die Info. Ich werde es weiter beobachten.
Alles Gute und 73 de Joachim.

Hallo, noch eine Frage: Kann man eine Verbesserung über "Noise Gate" oder "TX-Drive" erreichen.
Einstellungen: "Noise Gate" = 4
"TX-Drive" = 4

73 de Joachim

Forum rules: Language is English! Why? So that everybody can profit from everybody!

73 de Chris

Hello Joachim,

the most important thing is to speak loud and very near to the microphone.
There is no additional amplifier only the one in the elecret capsule itself and it is directly fed to the ADC of the MC. So if your signal is already very low at the input, the algorithm to calculate the appropriate good tx PWM is not capable to do without very high digital artefacts.... resulting in very bad modulation.

Yes you can play with and adjust the TX Drive, but normally if you have the Kit provided elecret mike you are okay with TX Drive = 4. You can also play with noise gate.
If the gain of the elecret is to low you can drill a hole at the microphone position to get more soundpressure in (I did this with a Baofeng trx, little bit louder and not so dump => more treeble).

One problem is not every Kit has the same elecret capsule due to part shortages.

73 de Chris

One thing i forgot:

If you try hearing/recording your own signal, take a dummyload on tx side, only a short piece of cable in the antenna connector (4mm "Bananenstecker" laboratory cable into SO239) or 60dB attenuator.
Another possibility: Use a WebSDR like:

http://websdr.ewi.utwente.nl:8901/

73 de Chris

Thanks for the information and now only in English.
73 de Joachim

Again on the topic of external microphones, with which make have the best success been achieved.
I fitted a Socobeta 3.5mm microphone to the uSDX.
Thank you and Merry Christmas.
73 de Joachim

I've had success using a Yaesu MH-34 and an adapter I built to the (tr)uSDX mic socket. I haven't (yet) wired up the speaker in the MH-34 but hte mic and PTT are working exactly as expected, and I've had reasonable readability reports.

I've also successfully used a cheapie Aliexpress special microphone wired for the RS-918 and McHF, again using another adapter I built to transpose the wires to the (tr)uSDX mic pinout.

While I've not yet tried any microphone that has a pinout that suits the (tr)uSDX without using an adapter I'm happy enough for the moment with my choices.

My recommendation would be
https://www.amazon.de/Retevis-Funkger%C ... 0865WPFXT/
as shown here:
https://www.youtube.com/watch?v=dEL74xyqwKM

73 Manuel, DL2MAN

Thanks for the information. Manuel's YouTube video is very interesting. Unfortunately, I don't have a 3D printer, but I have the option via an OM. Manuel, can you provide me with the CAD program for the connector housing.
Thanks and all the best
73 de Joachim

Just look in the Video description