Sticky: Post (tr)uSDX questions for the developers (Manuel DL2MAN and Guido PE1NNZ) in here

[wa2t]

...I would like to ask what role the 2060 and 86256 on the RF board play...

Hi,

Manuel answered the same question for me already (and so I will try to help out Manuel in return!). The two FET's you are asking about are not used and are "future use" for possibly having different RF PA device(s) than the current BS170's.

Hope this helps.

73,

Robert, WA2T

[wa2t]

...where it changed dynamically depending on the rotation speed...

I like this idea (but it's easy for me to say!).

73,

Robert, WA2T

[storyofyouandme]

Hello, Robert, wa2t, thank you very much for your reply. If you can, can you share the finished pictures of the motherboard and RF board? I want to know the direction of all the chips and those components are empty. thank you.
73.

[pe1nnz]

Hi Ferenc,

The filter bandwidth can be printed in a bit bigger font size, but doing so make things not better readable. I wanted to use the space around it to show other settings, but this might be overwhelming,

The idea of a variable step resolution based on rotation speed was tried out a while ago, but contrary to expectations it did not work that intuitive and consistently: sharp transition in tuning speed is experienced with the slightest change in turning speed, making it actually harder to tune.

More successful was the simulation of a very heavy rotary knob; a knob that once you turn at a certain speed it keeps turning at that speed and slowly slowing down in speed until you stop it by releasing a button, or when you give the rotary another speed. This way of tuning is pretty direct and controllable and is a great way to tune quickly over the band to scan for stations without too much effort. If there is interest, I can enable this in the beta version to try out.

73, Guido

[Kefeur]

Dear Robert!
That's the point and it can be simplified:
En_sped_1 = 50;
En_speed_2 = 100;
if (turned == 1) {
increment = first_speed_step;
currentMillis = millis ();
if (currentMillis - previousMillis <En_speed_2) {increment = Step_int_2; goto out; }
if (currentMillis - previousMillis <En_speed_1) {increment = Step_int_1;}
// else {increment = 10;} //
out:
previousMillis = currentMillis; }

[Andreas DJ3EI]

Hello,

and thank you for giving to the community this interesting rig and its concept!

I have some curious questions about it.

Your material says the rig has a class E PA and it also says it can transmit SSB. How so?

The only two ways of transmitting SSB with a class E PA I know are:

• Modulate the power supply voltage of the PA in a very elaborate way and at the same time carefully control the phase of the hf going into the PA.

• Restrict the incoming audio to a single frequency at a time at pretty much full amplitude, that is, transmit an AFSK signal.

I do not see the complicated stuff required for supply voltage modulation in the schematics. So I rule that out, this is not what you are doing.

On the other hand, there is a microphone, so AFSK is not what you are doing, either, or at least not the only thing.

Then, I saw a video with someone doing voice QSOs with the (tr)uSDX and claiming he transmits with 1 W power.

From that, I speculate you convert the PA from class E to class B (or maybe even A?) for SSB work, with the necessarily resulting reduction of efficiency and output power. Is that what you do?

I'm also curious: Does the rig support transmitting full power when audio with one frequency at a time is injected, e.g., the audio produced by WSJTX or JS8Call or the likes via a computer?

I'd appreciate if you'd kindly accommodate my curiosity.

Vy 73, Andreas, DJ3EI

[pe1nnz]

Hi Andreas,

In transmit the incoming audio is transformed into two components:
1. a power level to be set to the PA related to the incoming audio level;
2. an instantaneous single frequency (or sequence of frequencies) to transmit on, representing the correct phase of the incoming audio phase.

With this, a WSJTX single tone becomes a transmission on a single frequency with full power, and a voice signal becomes a SSB signal with varying power levels, but with the main portions of the transmission at maximum power.

In contrast to traditional PA drain modulation, this rig is applying a 5V RF square wave to the PA gate, but at different DC bias levels to regulate the power (DC bias ranging from 0 to 2.5V just below the gate threshold). This means that the top and bottom of the RF square wave at all times still operating the MOSFET as a switch, like is required for a class-E configuration, but the power level (the amount of current through the FET) is changing with the varying bias levels.

For voice in the near full or full modulation zone, the power is near maximum or maximum and result generally in the best efficiency of around 90%. At transitions of speech between full modulation and no modulation, the power consumption is reduced and the efficiency is degraded due to impedance mismatches with the class-E network and non-ideal DS resistance of the FET. As the duration of these transitions are generally only very short and make up only a fraction of the transmission, the overall average efficiency obtained approaches the 90%.

The main advantage of the technique described here is it's simplicity. It's also pretty fast/direct and efficient compared to the voltage loss and efficiency losses of a class-E (non-switching/analog) drain modulator. Disadvantage is the the non-linearity and temperature dependence, but this seems in practice a non-issue and something that can be compensated for in software.

73, Guido

[OE3DHB]

Hi Manuel, Guido,

first of all thanks a lot for this awesome project!
Yesterday I received my jlcpcb order of 10 boards and today I assembled one transceiver.

Now for my issue: Only the lower (80m) band is working when transmitting into a dummy load. I think already located the problem. The relays I am using have inverted set/reset states (FTR-B4GB4.5Z). I thought I checked this before ordering but it seems that all the +/- symbols really confused me
Would it be possible to include relay polarity as a menu item in the firmware? I can't think of an easy way of fixing this in hardware without replacing the relays.

Thanks
David

[pe1nnz]

Hi David,

Sorry to hear about the relays. Would a practical solution be to mount the relays on the bottom side of the LPF board?
This would correct the polarity of your relays without too much effort, but I am not sure if the boards still fit properly.

A feature to support reversed relays can be added, but makes only sense to do so when there is a majority that really needs the feature.

[Andreas DJ3EI]

In contrast to traditional PA drain modulation, this rig is applying a 5V RF square wave to the PA gate, but at different DC bias levels to regulate the power (DC bias ranging from 0 to 2.5V just below the gate threshold). This means that the top and bottom of the RF square wave at all times still operating the MOSFET as a switch, like is required for a class-E configuration, but the power level (the amount of current through the FET) is changing with the varying bias levels.

Hi, Guido,

wow! This is a slick idea indeed! And awesome you managed to make it actually work!

One could almost call this a new method for generating SSB!

Thank you very very much for the explanation. I love thinking about stuff like this.

Vy 73, Andreas, DJ3EI

[Faraaz VK4JJ]

Guido,

Please can you consider adding an option for a decimal point instead of commas (European style) e.g. as a number separator?

[storyofyouandme]

Hello, pe1nna

I noticed that dl2man is equipped with standing wave detection hardware, current monitoring and power and efficiency hardware, but these monitoring values of all DIY devices need to be calibrated. However, I did not find that there is a software menu for calibrating power, standing wave, efficiency and current in the firmware. There is no problem with open-source firmware, and the software can be modified. At present, the turusdx firmware of dl2man is not open-source, I hope to add a calibration menu. Otherwise, these test hardware can only be seen, and the practicability is not high. thank you.

73！

[pe1nnz]

Hi soyam,

Component variations in the circuitry of swr power, voltage and current measurement should introduce only a very small error and should have an unmeasurable effect on the results displayed in the uSDX. This means that calibration would not be necessary.

Did you build a (tr)usdx and see a significant error in the values displayed?

73, Guido

[DL2MAN]

(...) Otherwise, these test hardware can only be seen, and the practicability is not high. thank you.

The SWR Measurement consists of 2 equal transformers and doesn´t need to be calibrated. The current measurement hardware is "calibrated" by a defined trace lentgh on PCB. Whith 4 built units we did not see any significant differences.

73 Manuel; DL2MAN

[DL2MAN]

(...)
The relays I am using have inverted set/reset states (FTR-B4GB4.5Z).

As said before: With the (tr)uSDX we´ve created a standard set of hardware. The whole point of this was to make sure, we can concentrate on features instead of "hardware Variations".
So, when you thought you´d save some money and ordered different relays as we suggest you to use, and now ask for changing the software to adjust for your mistake, then this kind of proofs our point why it was good to fork off from uSDX...
Please invest the 20€ in a set of relays according to specs. This will solve the problem way faster, cheaper, and less stressful.

Thanks

73 Manuel; DL2MAN

[OE3DHB]

Please invest the 20€ in a set of relays according to specs. This will solve the problem way faster, cheaper, and less stressful.

Yes, you are totally right. I just ordered the right ones.

Thanks
David

[DL2MAN]

Thanks for your understanding, David !

73 Manuel; DL2MAN

[Vegaukr]

Dear Manuel and Guido, thank you for the great job! In my country 60m and 30 is not permitted for HAM radio. The idea is to use 160 m instead of 60 m and 15m and 10 m using the same modified 30 m band section. I think that such mod will be useful for many our colleges. So is it possible to provide LC parameters for this bands and plan to produce software option for this mod?
Best regards,
73! Vladimir

[DL2MAN]

Hello Vladimir,

Please refer to page 2 of this topic. It has already been answered.

73 Manuel DL2MAN

[storyofyouandme]

(...) Otherwise, these test hardware can only be seen, and the practicability is not high. thank you.

The SWR Measurement consists of 2 equal transformers and doesn´t need to be calibrated. The current measurement hardware is "calibrated" by a defined trace lentgh on PCB. Whith 4 built units we did not see any significant differences.

73 Manuel; DL2MAN

Hello, dl2man, I'm glad to receive your reply. I'd like to ask whether the power measurement option needs calibration. I found that there are calibration parameters in the early USDX firmware, which can be compared with commodity power meters for power calibration. Can you consider adding this menu, or the power measurement hardware of trusdx does not need calibration? Please answer it if you have time. Thank you.
73.

[storyofyouandme]

Hello, dl2man and all hams participating in this project on this forum, I would like to discuss the replacement of 3253 chips, because it is well known that JLC chips are out of stock and you can't get them through SMT. Under the background of continuous chip shortage, we may be able to buy one or two of them, Therefore, if a project wants to be healthy and sustainable, it is necessary for chip supply. Therefore, it is of practical significance for us to discuss the replacement of chips here. I hope that successful friends can experiment and replace them for reference. I believe most participants can't understand the parameters of the chip manufacturer's instructions, so I hope dl2man can add a line selection on its motherboard to adapt to these three chips. Here are some of my suggestions. Welcome to discuss and exchange. Thank you.
73

[Kazu.T]

Hi Guido,

Thank you for this great project, I really enjoy building the (tr)uSDX as well as porting your open source uSDX code to other MCUs.

I was looking for the menu "2.2 CW Tone" but not exist. After little reverse-engineering the (tr)uSDX firmware image, I realized that you didn't enable the "FILTER_700HZ" macro switch.

Do you have a plan to support this option?

As Manuel has suggested me in other thread, if I can help you in the firmware side, please let me know! I am more than happy to work on that.
Kazu. AG6NS

[storyofyouandme]

I carefully read the technical specifications of sn74cbt3253, sn74cbt3253c and fst3253mtcx, and also compared the sandwich motherboard drawing of dl2man and truusdx motherboard drawing. Personally, I think sn74cbt3253 \ sn74cbt3253c \ fst3253mtcx can be interchanged because the pins are consistent and the wiring of the drawing is consistent, unless limited by the new version of software. As for the 32 ohm speaker, I tried the 8 ohm speaker and used it the same way. In fact, this external speaker is more appropriate to be called headphone external, which is equivalent to a large headphone speaker. The disadvantage of both 32 ohm and 8 ohm speakers is that the sound is relatively small. You know, it cost me $4 to find this pair of 32 ohm trumpets, while the 8 ohm is only one twentieth of his. I hope it will help you.

73

[aloha]

For OLED display panel, why jumper from the input end (Vin) of U2 voltage stabilizing chip to C6? If the OLED display panel is not modified, what will be the problem? thank you

[DL2MAN]

@storyofyouandme:
As you figured out, there´s plenty of alternatives available for the 3253. We do not want to deviate from that, as this is supposed to be a "standard". This is a general statement: The hardware is SET and will only be changed for good reasons, not for saving a few cents, not for convenience, not for "i like that one better".... Noone is forced to follow our suggestions, but we´ve tested it the way we rolled it out, so we know it works. Any deviation from that needs to be tested, documented etc... And if you deviate, and have problems you´re on your own.
Regarding speakers: 8 Ohms can be used, but put the ATMega to it´s current limit 2 Volume Steps earlier compared to 32 Ohm Speaker. For 32 Ohms -> Max Volume Setting is 15 for 40mA Current Draw per Port. For 8 Ohms, this limit is already reached at Volume Level 12-13.

@aloha:
Removing the 2 Capacitors disables the "Charge Pump", an on board DC Upconverter. The wire supplies the OLED with clean 5V. The mod is neccessary, because otherwise you could hear your OLED in the receiver... OLEDs are known to be noisy and this way we get around that.

73 Manuel; DL2MAN