Products > Test Equipment
FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
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aimc:
That's interesting! Yeah the trig out of the FY does not make much sense for any sweep or VCO operation which kind of sucks. Otherwise it looks like you are getting similar results for the F...T brand while the Keysight seems much better. Your Keysight manual boasts with +-0.2dB amplitude flatness, so it better be. Looks like your time base and VCO sweep was faster than I did because your jaggies are bigger and you can't see that the response has a slight s-shape. A bit concerning as you say is the sampling rate in both our cases @60MHz. You used 5MSa/s and I used 20MSa/s which is grossly under sampled. However, it should not impact in the amplitude per say. If you have enough periods and non-integer multiple sampling points (you don't because you sweep) the lower frequency alias amplitude will at least be as high as the signal. This is covered by sampling theory. To demonstrate I repeated the experiment with 100MSa/s (I know its not >120MSa/s as it should be but close enough when using sinc interpolation, see aliasing in attachment "..no_SINC")  and found the drop being almost the same as with my former under-sampled post. For this reason alone I think the FFT method is likely better as you are using well oversampled small sweep-time pieces for each FFT. But there you have imprecisions with the windowing. So nothing seems better than the good old simple peak detector (or any new-fangled detector you can buy from Analog Devices).

If you don't trust me, you can try a higher sampling rate - but I think at the end of the day you measure the same drop...

Thanks and cheers
Lutz
CDaniel:

--- Quote from: fremen67 on September 22, 2019, 12:13:40 pm ---
--- Quote from: CDaniel on September 22, 2019, 07:50:56 am --- I have v3.1 , the firmware will work ?

--- End quote ---
Yes it will. I tested it with flash eeproms v3.1 and V3.2.
It doesn't work with a V3.3 eeprom but as I don't have a V3.3 front panel, I can't see what changed in the FP-FPGA protocol for v3.3.

--- End quote ---

Hello , I flashed a spare microcontroller with your firmware ... quick bug , in sinewave the output is badly distorted if I go up in frequency up to 197KHz . If I go back down from here is OK untill 1KHz or something when the distortion appears again . Something in comunication with the FPGA is not quite right .
fremen67:

--- Quote from: CDaniel on September 30, 2019, 05:35:54 am ---
--- Quote from: fremen67 on September 22, 2019, 12:13:40 pm ---
--- Quote from: CDaniel on September 22, 2019, 07:50:56 am --- I have v3.1 , the firmware will work ?

--- End quote ---
Yes it will. I tested it with flash eeproms v3.1 and V3.2.
It doesn't work with a V3.3 eeprom but as I don't have a V3.3 front panel, I can't see what changed in the FP-FPGA protocol for v3.3.

--- End quote ---

Hello , I flashed a spare microcontroller with your firmware ... quick bug , in sinewave the output is badly distorted if I go up in frequency up to 197KHz . If I go back down from here is OK untill 1KHz or something when the distortion appears again . Something in comunication with the FPGA is not quite right .

--- End quote ---

Hello, did you swap the microcontrollers?
I tested with my 2 FY6600s. One has a swapped MCU, the other has a bluepill… Sorry but I can't reproduce your problem  :-//
The sines are normal till 62.5 Mhz…
The MCU is not supposed to have an impact on sine output or shape. It just send the parameters to the FPGA when you change them but then no communication anymore with the FPGA.
Could you also test with an ARB sine (ARB1 if you did not change it otherwise you can create one and send it with PC Software).

Do others have the same problem? DaveR, Soundtec, jleg??

fremen67:

--- Quote from: Miti on September 26, 2019, 02:26:42 am ---Hi Fremen67 and welcome back! I surely hope that you were just busy and nothing tragic happened.

--- End quote ---
Thank you! Well... death is part of life… time eases things...


--- Quote from: Miti on September 26, 2019, 02:26:42 am ---How may I help to figure out V3.3 and what do I need? My FY6600 is V3.3. I don't have a logic analyzer but I do have a Rigol DS1054Z. Probably not enough, eh?

--- End quote ---
You can do things with a DS1054Z but I am afraid the only reasonable way is the logic analyzer.
CDaniel:
OK , sorry about what I said , no bug , I forgot to connect a wire and the analog part wasn't properly powered . My FY6600 power supply is modified and uses a PWM signal from the microcontroller .
Yes , the original microcontroller is swapped with another one .

Just a sugestion , the frequency displayed is still hard to follow with just one decimal point when it is in MHz range for example ... I have to count allways how many digits are before the dot  ;D . Would be nice to display MHz , KHz and to move the point accordingly .

The sub-hertz many many digits ;D I think shouldn't be displayed when are not used ( set to 0 ) .

If you go to the max with the tens of MHz digit ( by error or not ) , the rest of the display goes to max also  and you lose what you have set , maybe you want 59.123456MHz . I think would be better not to let you go beyond 5 if 6 and the rest of the digits would be an invalid frequency .
When you go down in frequency the same thing happens if you reach 0 and turn the encoder one more time , the rest of the digits are erased to zero , I don't think this is desirable . Zeroing the display could be usefull , but with a long press on the encoder or another combination when you are in frequency adjustment .
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