Digital Modes Rig - Part 1 Design Thoughts
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- Опубліковано 30 вер 2024
- Video looking at the design thoughts for a general digital modes rig. The aim is to build a Teensy based USB rig using the phasing technique. The aim is to have CAT control (FT-818 protocol) and an output power of 5W or thereabouts.
Did you consider doing digital modulations directly with the VFO chip? There's a library for Si5351 which takes care of modulation.
No Sajjad, but it is something I want to do at some stage. It's on my list.
Hi Charlie,
firstly if you check in the manage libraries ( in the arduino IDE ) you will see a cat control for a Yaesu 857D... this will setup the arduino/teensy to be seen as a yaesu 857D radio. Thats your cat control protocol sorted even if its not an FT-818. The teensy can be put into the "serial/midi/audio mode" usb interface mode. This has the side effect of giving you a soundcard and serial right on a single usb cable. i hope this small piece of information gives you a good start on a possible direction with the software/hardware.
Best regards
Simon
Thanks Simon. That is really interesting thanks. I have not used the Teensy in the audio mode, so that will be interesting. Thanks very much for the steer.
@@CharlieMorrisZL2CTM it's no harder than you already have done just look for the usb in and out modules in the audio design tool. then just patch cord the usb in to the line out and the line in to the usb out module. I have just finished a quick experiment with my own code in a teensy 3.6 and have passed the test cat function and have set both audio in and out to "digital audio interface (teensy midi/audio)" at the same time. i May finish the code off and get a working cat interface or emulated yaesu ft-857. Emulated cat functions for at least the basics of frequency and tx.
best regards
Simon
Hi Charlie, did you sort out that cat library and get it working? I have a piece of software that's almost finished for the teensy 3 boards. I have it partially working for the yaesu radio's... there is a group of radio's that it will work with
Best regards
Simon M6FJW
since it is FT8 you may go for a non-linear PA like a class C single transistor amplifier. Maybe even test some VHF BJTs like good old 2SC1947, 2N2078, BLY91 or 2SC2101 or similar types that have more gain and output power in HF, of course with proper feedback.
Thanks. I'll look into that.
Have you made any radios using a QSD/QSE/Tayloe mixer, that seems like it could be a good fit here. I have also heard good things about H-mode mixers, but don't know too much about them.
I like the suggestions others made about being able to combine the audio and serial control over a single USB cable with the Teensy. I didn't even know that was possible.
I don't remember if it was from your other SDR videos or somewhere else, but I have seen some DSP phasing use two 45 degree shifts, with one for the I signal and one for the Q signal, which still creates a 180 degree phase shift between the two. The reason for that was so that both paths have the same latency, instead of only the Q path having latency added when the 90 degree shift is applied.
I look forward to seeing how this progresses.
Hi Rob. Yes, i have played around with the Tayloe mixer a while back. It certainly worked well. More recently I have elected to use the double direct conversion mixer approach. I didn't know about the audio and serial control for the Teensy either. I hope I can make that work. As for +/- 45 degrees. That's what I use for the SDR radios. The Iowa Hills filter design software suggests that is the best way for the reason you outlined. Otherwise, you need a fixed delay in the I signal line to match the latency. I didn't mention that in the simple diagram as not to muddy the waters so to speak. Hopefully today I can get WSJT-X to recognise the Teensy running the FT-857D software library example sketch as a valid radio. It wasn't last night, which was a pain!
Charlie, you can certainly input non-standard frequencies in WSJT-X. I haven't tried tuning the rig to see if WSJT-X tracks it. I have been using a small laptop with USB to USB-C convertor for CAT control and an audio plug splitter with the audio signals going through an old PSK interface with opto-isolators and level controls. I did have issues with stray RF upsetting the USB but some ferrite on the various leads sorted that. Looking forward to seeing your rig develop.
Stanks Steve. I have the CAT mostly running, which is good. Once I have that fully functional I'll be able to fully evaluate WSJT-X. I don't have a CAT capable radio at the moment, which makes it difficult. Thanks again.
Look at the July 2020 QEX to see a decent breakdown of FT8/FT4 and how it is in the implementation.
Cheers Robert. I'll take a look.
Yes, in the newer CAT control, it is bidirectional. I have a Yaesu FT-757GX, and it has cat control (a very early version of it), but it's only one way. So, the new CAT control, is bidirectional.
You were discussing in the video whether you would use NE612's or some other mixer. My vote is with the 612's. They're much maligned as Rx mixers but I think the requirements are different here. 612's seem to be pretty easy to get your hands on at least around here so others can follow your lead.
I 2nd the suggestion to try and get the audio over USB as well as the CAT "serial". The nice thing is you can do this in stages. Get the project working using traditional speaker/mike connections then transition to USB audio. This should be made easier by that excellent Teensy audio library and design tool you mentioned.
That's what I am thinking too Dave. I get a bit of conversion gain at the same time, which would be good.
@@CharlieMorrisZL2CTM On this project could you explain your thinking around gain and losses through the various stages? I certainly get the concept (you need enough drive out of one stage to satisfy the input requiremenst of the next stage) and you often mention this with some explaination but I'm interested in hearing more about your thinking on the subject.
Thanks
Do you have a book or planning to make one on building and designing a transceiver? For educational and experimental purposes, this material seems to be very valuable. Thanks. 73
No not at this stage. I have been asked the same thing a few times now. I'll have to put some thought into it. Charlie
@@CharlieMorrisZL2CTM Sure, and also courses on Udemy, those will be nice too. Check it out.
I think it would be entirely doable to control the frequency from the computer. Even if the software for what ever digital mode you are using can’t control it directly you could write a bit of software that would allow you to control the radio from a different window.
It makes some sense to use the existing audio input and output of the computer and the usb-c for CAT control. Certainly easier. But have you considered a splitter on the usb-c to allow both cat control and a sound card through a single cable. I guess I am trying to get you to build black box with a single cable connection instead of the three you are planning. The trade off is that you will spend considerable time figuring out a sound card interface and cat interface which might be further away from you desire to do RF engineering. That is the drawback or advantage of these SDR rigs. Simpler electronics traded for rather complicated software. Best of luck. Charlie KM4ZZ
Thanks Charlie. I like software engineering too, so that's not a problem. It should be fun.
Don't use the USB serial adapter for cat control, the teensy can easily handle that. You should be able to "emulate" a sound card and a serial port with the teensy 3.5 and still have room to spare.
Thanks Tim. I will try and get that to work. At the moment I am testing the Arduino FT-857D library, but cannot get WSJT-X to see it. I'll get that working first and go from there.
@@CharlieMorrisZL2CTM " device monitoring studio " is a good free software to monitor the serial port .. so you can figure out what is going on ... the operating manual of FT857 have a full detail of CAT command and example
www.passion-radio.com/index.php?controller=attachment&id_attachment=288
Looking like a plan. I did play around with the CAT interface on my Icom a few years ago, was a little odd in that it was using only a single wire for both rx and rx but it did work. Not sure of the Yaesu configuration but I'm sure you'll get it working.
Will you be driving the NE612's with quadrature signals directly from the SI5351 board. I'll be following with interest.
73 for now.....
Thanks Brian. Yes, I will generate the quadrature LO signals straight from the Si5351. Just struggling to get WSJT-X to see the Arduino FT-857D example sketch. Rome wasn't built in a day as they say.
@@CharlieMorrisZL2CTM Might want to take a look at the source from the ubitx. It shows up as a some Yeasu to WSJT-X.
Looking forward to the progress on this - particularly the CAT control side of things. Having the entire UI on the computer makes a lot of sense!
Cheers. Would you agree that there is no need for a rotary encoder and display? I'm inclined to think it can all be done in-say-WSJT-X and the like.
@@CharlieMorrisZL2CTM I think so - I have never programmed to the CAT interface so not sure on the acknowledgment demands and how complex that is to deal with though. What you may want to retain though is some way of controlling the calibration of your radio - that frequency emitted by the si5351 is always out! Maybe also you'll need to calibrate the phase shift perhaps. Cool stuff indeed.
One thing I thought I would ask though is did you consider using FST3253s as mixers (the "Tayloe" detector) I have always had success with them in IQ style radios
Hi all .. i think you have to use the rotary encoder but not the display ... I'm using JTDX software with my IC7100 ... the CAT control is bidirectional you will get the freq. on the software ... the same with WSJTX
the software have a freq. list that you can select from ... but you cant tune around like a VFO ... you can add a new freq. to the list that's in the setting ... and during operation you can select it from the drop menu ....
Super waiting for next video/stage
Thanks. Just working on the CAT code now. I'm going to make it look like a K2 if I can.