(tr)uSDX Forum

Hi Group,

Last night, I tried WebSDR with my (tr)uSDX and SSB really did not sound any better to me. But, as I was tuning around, I found W9IMS (Indianapolis Motor Speedway special event station) on 7.240MHz and called him with about 655W (using my RF2K+ LDMOS power amp and the (tr)uSDX). I was using my modified Baofeng speaker mic. He responded with a 59 and said I was very strong. I did not ask specifically how my audio was (I should have) but obviously I was intelligible enough for him to complete the exchange. So, this has changed my feeling a bit on SSB with the (tr)uSDX - for the better. It will never be as good as a more traditional SSB XCVR, but it does work. Your mileage may vary...

73,

Robert, WA2T

Magnus wrote: ↑27 May 2022, 22:40 I just got my assembled (tr) usdx, om 20 m there is a small carrier wave transmitted even though the unit is om recieve.

If you put two receivers next to each other on the same table, it's not uncommon for each to hear the other's LO, due to PCB to PCB or case to case parasitics. (Except for direct sampling rigs, where the LO might only exists virtually in software). 73, Ron

I seem to be having this issue. I opened up my radio kit I had purchased from Amazon
https://www.amazon.com/dp/B09YH2V2ZP and assembled, and I do seem to have the preferred OpAmp. I'm still seeing quite bad splatter similar to what KB9RLW sees in his radio shown in this youtube video. https://youtu.be/UWcDLq0WM1o?t=237

I'm curious if maybe there is some tuning in software that I could maybe try. I've tried testing with an external mic as well and see the same results, so I don't think its that the mic has a short causing weirdness.



EDIT: Some clarification. I've been testing by transmitting about 0.5w into a dummy load and receiving the signal on a very close proximity SDR ~1 meter away from the tr usdx.

In the Titel mentioned Sideband suppression is an rx issue.
What Kevin and you are seeing, is a nearfield Effect of tx. Add at least 60dB attenuation between (tr)uSDX and Control rx.

Here is a Text that disappeared from the YouTube comments (Not caused by Kevin):

Guido and me were joking today about a start up message, that says never test (tr)uSDX Audio in near field.

On a near-field receiver, the SSB signal is so strong that the small artefacts of the digitally processed signal in the (tr)uSDX becomes audible. In a normal QSO setting there is so much path-loss involved that these artefacts are well attenuated below the noise floor and hence not observable.

Note that every signal that is digitally processed has this limitation, it is called quantisation noise and these are noise signals in the background of the main signal. It is only when you start amplifying the signal that this noise becomes apparently observable.

To test the SSB/AM signals on a near-field receiver, the recommendation would be to use an attenuator of 60dB or more in-front of the receiver. Watch for proper shielding along the whole path, so RF does not escape your dummy load. Best is still to access a remote receiver and check your audio. You will see the difference immediately.

73 Manuel DL2MAN

Just wanted to follow up on my previous query. After watching your video https://youtu.be/dHttnDdADqo I flashed my bootloader and firmware fresh to test this. I've only been able to test on 40m into a WebSDR about 450km from me and to my very local personal SDR. The splatter locally appears to be much less and splatter and readability into the WebSDR is *much much* better. Just wanted to give you another data point.

I'm confused how the bootloader could affect splatter, but in any case I'm more comfortable using this radio now and not worrying about interfering with my spectrum neighbours. Thanks DL2MAN!

Dear colleagues, I immediately apologize for my indiscretion, but it makes no sense to override the operational amplifiers, you just need to connect 1uF capacitors in series with 100 ohm resistors to the inverting inputs on pins 2 and 6 and the mirror channel disappears on all ranges including 10m

who can please let me know

Dear colleagues, despite the fact that my messages are deleted due to the fact that I am from Russia, I will once again tell you how to modify the usdx receiver so that the non-working sideband is suppressed, I have already done this and everything works from 80m-10m. just add two 1uf capacitors in series with 100ohm resistors connected to 2.6 pins of the op amp

please listen to me and get rid of the problem of suppressing the non-working side

Ra9oau wrote: ↑30 Nov 2022, 07:49 Dear colleagues, despite the fact that my messages are deleted due to the fact that I am from Russia,

Are you a little paranoid ? Noone here has deleted anything. There are 4 postings in a row from you. Visible for anyone. I know you´re having a hard time with borders, but please be careful with such accusations.....

Ra9oau wrote: ↑30 Nov 2022, 07:49 I will once again tell you how to modify the usdx receiver so that the non-working sideband is suppressed, I have already done this and everything works from 80m-10m. just add two 1uf capacitors in series with 100ohm resistors connected to 2.6 pins of the op amp

Thanks ! We will try that.

73 Manuel, DL2MAN

I deeply apologize for what I wrote, but there is no paranoia, I just didn’t understand the chat and didn’t find my messages, but since the political situation in Russia and border states is very complicated, I thought that my messages were deleted. once again I apologize

https://youtube.com/shorts/9L0xI-mmDig?feature=share there are still improvements to the transmitter, a demonstration on the video, and somewhere in the comments there is a google disk 0 link to other improvements

What minimum voltage rating is needed here?
Do you need to use a film cap or an npo/cog cap? Will an electrolytic do?
Can you use a X7R cap? (0805 and 0603 available)

Is this only for reception or does it cure the "splatter" transmit audio problem found in some units?

And does it officially work?

“Thanks ! We will try that.”
So,I am confused, was this a joke or was it serious???

Ohwenzelph wrote: ↑05 Dec 2022, 15:35 “Thanks ! We will try that.”
So,I am confused, was this a joke or was it serious???

This was not a joke, I simply have no rig, that is affected. It´s hard to test if a problem is gone, that was not there in the first place.... So I´m waiting for the right moment, or rig, or whatever.
At this point of the circuit, we have 5V, so at least 6,3V Rating would be required.
Regarding dieclectricum or technology, I would not mind testing anything, that is available.

73 Manuel; DL2MAN

no, this is not a joke, there is suppression of a non-working side from 80m-40m, it is better to install capacitors with non-polar ceramics or film, but this is unprincipled.

Sorry 80m-10m

Hi Ra9oau

The drive location you linked is for the uSDX, not the (tr)uSDX.

Was this deliberate?
The linked files are apparently not relevant to this particular project, as this project is a further development of that project.

Unless, I've missed something here.

-Cathal

да эта ссылка для usdx единственное что вам там не подойдет это переключатель диапазонов на 74hc595 потому что я переписывал управление lpf для себя а модернизация выходного усилителя подойдет всем главное найти место в корпусе.

transmission distortion disappears even in the near field

Yes, this link is for usdx, the only thing that will not work for you there is the range switch on 74hc595 because I rewrote the lpf control for myself, and upgrading the output amplifier will suit everyone, the main thing is to find a place in the case.

I'm sorry, I wrote in Russian, not everyone will understand

Are there any differences between uSdx and (tr) uSDX?

the schemes are the same, and if there are differences, then very small