SP3OSJ
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OVI 40 canal I/Q (RX)
« on: 13. April 2018, 12:30:10 »
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Sound in OVI40 channels is different for channel I for channel Q
Is this good?
Maybe this is the reason why RX has more noise in OVI40 than with the mcHF controller.
A movie with this problem:
https://youtu.be/moNGCHZxbyM
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DB4PLE
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Re:OVI 40 canal I/Q (RX)
« Reply #1 on: 13. April 2018, 13:44:56 »
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Hi,
interesting, but you do think this is a problem of your particular hardware or do you think this is a OVI40 design problem (it could also be a software problem, but I checked the code and it is identical in that respect for mcHF and OVI40)?
73
Danilo
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SP3OSJ
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Re:OVI 40 canal I/Q (RX)
« Reply #3 on: 13. April 2018, 14:22:02 »
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After connecting the PCB RF the radio is working properly.
A good SSB signal (USB and LSB) is decoded
PCB RF connected to the mcHF controller gives less noise
than the same RF PCB connected to the OVI40 controller.
Why?
LCD is more noise and more noise other processor?
Is this a software error?
Check if the controller has the same noise (I/Q) at the converter A/D (RX) input (speaker).
I will be fine if I have a problem 
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| « Last Edit: 13. April 2018, 14:30:55 by SP3OSJ » |
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DB4PLE
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Re:OVI 40 canal I/Q (RX)
« Reply #6 on: 13. April 2018, 20:18:54 »
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Hi,
just did an experiment:
Connected same RF board to dummy load, and then use a mcHF 0.4 UI 3.2 display SPI 320x240 and a OVI40 UI parallel display with 480x320 on it using the same frequency and mode, filter etc. settings.
dbm/hz for mcHF 0.4 -> -144, OVI40 -> -123 . But wait: Now I applied a well known source of noise (an antenna)
dbm/hz for mcHF 0.4 -> -114, OVI40 -> -98
Assuming that both get same signal. Now I calibrate both to show -98 dbm/Hz. And repeat above measurement, now (no surprise here) the mcHF has -128 dbm/Hz and the OVI40 has still -123. That is only 5db difference. While still significant, nowhere near has high as shown.
Unfortunately, my display & heat sink construction makes it difficult to measure the individual channels as asked for.
73
Danilo
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DB4PLE
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Re:OVI 40 canal I/Q (RX)
« Reply #8 on: 14. April 2018, 10:03:36 »
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Hi,
btw, I should have mentioned, that I have used a OVI40 H7 to run the test, not the normal OVI49 F7 (which I have in a case, so it is hard to use the same RF board for testing. The STM32H7 runs with 400 Mhz and this indeed might cause some extra noise being generated.
73
Danilo
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SP3OSJ
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Re:OVI 40 canal I/Q (RX)
« Reply #9 on: 14. April 2018, 12:41:38 »
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Andreas is your mcHF does he have a helicopter? all bands, all freq.
The effect on the movie causes the function:
Menu/Configuration Menu/RX IQ Auto Correction -> ON
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DD4WH
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Re:OVI 40 canal I/Q (RX)
« Reply #10 on: 14. April 2018, 13:43:56 »
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Hi Artur,
very interesting observations that you made!
I am not sure if you observe the same thing if auto IQ correction is OFF?
The auto IQ phase and amplitude correction algorithm is programmed to be quite slow. It needs nearly one second until it is settled, because of the small alpha in the lowpass filter which smooths the determination of phase and amplitude errors.
The difference in reaction of mcHF and OVI40 UI PCBs could be explained by different intitial phase and amplitude errors introduced by the PCB layout --> just guessing here.
However, that cannot explain why Andreas measures 5dB better performance of OVI40 and Danilo measured 5dB better performance of mcHF . . . but that may be the interaction between UI and RF boards? Andreas uses his own RF board and Danilo uses mcHF RF board. Too many variables here ;-).
All the best 73s
Frank DD4WH
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Teensy Convolution SDR
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DD4WH
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Re:OVI 40 canal I/Q (RX)
« Reply #11 on: 14. April 2018, 14:03:15 »
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oh, just had two other ideas!
1. PROBLEM WITH DIFFERENT FFT SIZES FOR SPECTRUM DISPLAY COULD INFLUENCE MEASUREMENT PERFORMANCE
mcHF UI --> small TFT --> spectrum has resolution of 256 (small FFT)
OVI40 UI --> large TFT --> spectrum has resolution of 512 (large FFT)
Maybe we have a problem with our measurements of the signal and not with the UI board influencing the RF performance?
I have not deeply thought about how a doubled FFT size might influence the dBm measurements, but my suspicion is that the cause of the different figures could be the software measurement procedure itself.
We have to look at the dBm code and also perform test measurements with very low signal strengths.
2. DO NOT BELIEVE IN THE ACCURACY OF DBM MEASUREMENTS IN SSB BANDWIDTH WHICH ARE LOWER THAN -102dBm
Christian, DL9NL has shown nicely and very precisely that the mcHF is capable of measuring signals down to -102dBm (SSB-bandwidth 2.4k) accurately --> forget measuring lower signals in SSB bandwidth accurately! In CW bandwidth (300 Hz), signals can be measured accurately down to -119dBm, but not lower.
http://funkamateure-dresden-ov-s06.de/index.php?article_id=462&clang=0
But in our thread here, signals in SSB bandwidth are compared which are as low as -123dBm (or even lower) --> let us not believe these figures. The mcHF/OVI40 is NOT a measurement receiver capable of measuring accurately such extremely low signals . . .
73 Frank DD4WH
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Teensy Convolution SDR
https://github.com/DD4WH/Teensy-ConvolutionSDR
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SP3OSJ
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Re:OVI 40 canal I/Q (RX)
« Reply #12 on: 14. April 2018, 14:07:20 »
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Franc
Andreas measures mcHF on the "helicopter".
I do not have a helicopter at mcHF
I do not have a helicopter in OVI40
Danilo and Reto (HB9TRT) has good measurements.
My opinion is this.
If Andreas does a "super" RF to VIO40, then this "super" RF PCB will be even better on the mcHF controller - if it's compatible.
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| « Last Edit: 14. April 2018, 14:20:02 by SP3OSJ » |
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SP3OSJ
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Re:OVI 40 canal I/Q (RX)
« Reply #14 on: 14. April 2018, 17:52:59 »
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mcHF / OV40 has very poor converters AC/CA WM8731 (TLV320AIC23), CS4272 is much better.
See this movie:
https://www.youtube.com/watch?v=mrf9BsNrIHc&t=318s
Listen, what's the noise.
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Author
_I_Q_.JPG
