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FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator

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soundtec:
Many thanks for the detailed reply Fremen,

I do wonder though are all the internal factory stored waveforms subject to this degradation over time , it was only my abillity to measure very small amounts of distortion was I able to detect it . The great thing for me is that my FY6600 is now capable of even lower distortion on sine waves than before ,and by a good margin , I was in 0.05 % territory now with the new sine  its more like 0.002% or less 2nd harmonic , as well as upper harmonics barely above noise floor .

DaveR:
Hi Fremen,

The software checking is still in progress, but I've been through quite a bit so far and only come up with one crash and a couple of small items:

Calibration:  Ch2 Offset M:2.5 - this gives a Runtime error 6 if you try to enter a value less than 2.5, so the allowable range needs to be checked.  The program closes when the error dialog is cleared, but the entered value is still saved.  Once, after restarting the program after this crash, the boxes in the Control Window were full of improbable and impossible values, so data corruption had obviously taken place again; the same incorrect values reappeared each time the program was restarted, whether set to Defaults or M1,  but at least the program still ran ok and sensible values could be entered in the value boxes.  I couldn't recreate this situation again, so hopefully it was just a one-off.

Control Window - Sweep - Square Wave - Duty:  Ch1 range is 0.001% - 99.999%, but Ch2 range is only 0.1% - 99.9%.

Control Window - Ch1 Mod - FSK - HOP Frequency has redundant decimal point after value if whole number entered.

All the previous problems have been cleared, and waveform uploading now works very well indeed.  I need another session or two just to recheck the sweep and counter functions, but it's looking pretty good at the moment!

Regards,
Dave

fisafisa:
Hi
No more news?


Prehistoricman:
Did you guys ever extract the built-in firmware?

I found this paper that extracted firmware from an STM32F1 series MCU 'easily':
https://tches.iacr.org/index.php/TCHES/article/download/7390/6562/
Page 9/10 (207/208)

Sounds like a fun project.

Edit:
And by an interesting coincidence, this paper specifies a FeelTech unit for generating their attack glitches.

wpmcnamara:

--- Quote from: bdunham7 on June 11, 2019, 11:52:29 pm ---
--- Quote from: vince53 on June 11, 2019, 07:18:52 pm ---
I used it to align some AM radios but now I wanted to align the 10.7MHz IF sections.

So I recently purchased an FY6800.  After verifying it worked I ordered an assortment of upgrade parts.  I installed a linear 15vdc supply, installed new op amps and replaced the encoder so I could have a larger knob.  Next was to figure out how to get a repeatable setup for FM IF sweeps and contribute to the thread.


--- End quote ---

I also want to repair/restore/adjust/align/fiddle with some FM receivers.  I'd be interested how you make out.  Is it necessary to have such high outputs that new power supplies, op-amps, etc are needed? 
Also, I'm trying to synthesize a usable FM multiplex stereo test signal.  I have an RF signal generator with an FM function, but the multiplex signal is complex and I'm still trying to figure out the best way to do it.  Any ideas?

--- End quote ---

I recently picked up a FY6800 cheap and the first serious thing I did was use it in troubleshooting an AM/FM receiver.  You can generate a basic, but very usable stereo FM IF signal with the 6800, straight out of the box, no mods necessary.  I loaded a stereo multiplex signal in one of the arbitrary slots and used it, on channel 2, to modulate a 10.7 MHz sine wave on channel one, which I fed into the IF section.

The stereo MPX isn't as complicated as it sounds.  I put together an Excel spreadsheet that would generate the waveform for me.  8192 data points is plenty.  I generated a cosine signal on the left channel and a sine signal on the right.  The spreadsheet lets me adjust the L and R levels, as well as the relative modulation levels.

This is the MPX signal for a 1kHz sine and cosine at equal levels.


This is what the decode output looks like.  This was taken from the audio outputs on the receiver sitting on my bench.


Similarly, this is the MPX for a 1kHz sine and cosign with one signal at 50% of the other.


And the decoded output...


Now, you do see some channel separation problems if you set on channel to 100% and the other to 0%.  Channel separation is only about 20dB in that case.  However I don't know if that is a problem with the spreadsheet math, the limited sample size of the waveform, or this particular receiver.

*edit*  attached spreadsheet I used for the MPX waveform generation.

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