SDRplay gain bug with FMPP 1.13?

GM8ARV

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Jun 29, 2020
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Setting IF gain to "-M11" in the batch file isn't honoured immediately. Although the spectrum caption says "IF: 11 dB", it's actually much higher. Pressing "k" then "K" restores the correct gain (as seen on the spectrum). The gain appears to be the equivalent of IF: 48 dB at startup.

Tested with FMPP 1.13 and API 3.06. Using RSP1A RSP2 or RSPdx devices shows the same behaviour.
 

N6ML

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Same here (with an RSPdx). Did you get anywhere with this? Try to contact DSDPlus support directly?
 

N6ML

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The other thing I've noticed is that the "sampling rate" option in FMPP.cfg seems to be ignored - it always uses 3.0 no matter what I put in there. Do you see that too?
 

GM8ARV

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The other thing I've noticed is that the "sampling rate" option in FMPP.cfg seems to be ignored - it always uses 3.0 no matter what I put in there. Do you see that too?
I've not checked that, and the system is not available currently as I'm merging two old PCs into one new one, and that's filling all the time!
 

wgbecks

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Same here (with an RSPdx). Did you get anywhere with this? Try to contact DSDPlus support directly?
Same results with my RSPdx. Additionally, FMPP dosn't allow for PPM adjustment (calibration) were my RSPdx is off frequency 304 Hz at 853 MHz with no way to make corrections. Decoded audo quality is very degraded as compared to my Airspy Mini that I have calibrated to be within +/- 10 Hz at 853 MHz.

Yet another issue with FMPP is that the bandwidth keeps reverting to 9.5 KHz upon retuning (single sdr) to the first channel grant from
the initial -b12.5 setting. This of itself would not be nearly be of concern except that there is no way to trim the RSP's to frequency whereby
the narrower bandwidth override of FMPP contributes to additonal decoding errors.

This exact behavior exists with FMPA when using Airspy R2's or Mini's. But at least you can calibrate the SDR to frequency using Airspy's
calibrate utiilty to trim the SDR to frequency negating the effects of the narrower bandwidth filter auto-override.


Bill
 

wgbecks

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Update: I sent off an email today to the DSDPlus Fast Lane development team.

DsdPlus Fast Lane development team:

I am writing to report bugs and operational deficiencies with FMPP 1.13 in the operation with SDRplay_RSP_API_Windows-3.06.

User Hardware/Software Configuration

Lenovo T450s i7 8GB
Microsoft Windows-10 Professional Version 1910
SDRPlay RSPdx
FMPP 1.13
DSD+ 2.256

FMPP-CC (batch file)

FMPP -rc -i1 -o20001 -L8 -M0 -v80 -b12.5 -f853.925 -_3
  1. FMPP initializes with maximum IF gain despite initial fixed gain setting of -L8 -M0 in my FMPP-CC.bat file.
  2. FMPP does not respond to user specified sampling rate specified in the FMPP.cfg file.
  3. FMPP overrides user specified bandwidth of 12.5 KHz with a value of 9.5 KHz upon following the first P25 channel grant.
  4. FMPP has no provision to pass PPM corrections via the API to the RSPdx attached device.
There is a work around procedure for the initial IF Gain issue (1) reported User can press “Active Key “K” upon startup of FMPP
to restore IF Gain to user specified value.

FMPP Initial IF Gain Startup Error

RSPdx-1.jpg

FMPP IF Gain Following Manual Correction with Active Key Press “K”

RSPdx-2.jpg
 

EricCottrell

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Hello,

I sent off my observations months ago to the DSDplus and got a response back that there are no problems. I was able to test the different RSP models. I think the DSDplus development team wrote FMPP to support the RSP2 and just left it. It seems FMPP is only updated to the latest API without really considering the other API changes. FMPP seems to only know about the RSP2 gain settings.

There is no squelch logic control (-q) and scanner mode (-s) does not seem to work.

No bias tee support for the RSPduo, RSP1A, and RSPdx.

On the RSP1A, the Antenna Select and Notch Filters controls seems to disconnect the antenna. I get a spectrum with no signals.

On the RSPduo, both antenna inputs are active. The Antenna Select and Notch Filters cause a freeze and restart of the input stream.

On the RSPdx, both antenna inputs are active with Antenna A being more sensitive. The notch filters seems to work. The Antenna Select seems to disconnect the antenna. I get a spectrum with no signals.

73 Eric
 

wgbecks

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Jan 17, 2005
Messages
255
Location
Porterfield, Wisconsin
I could live with the initial startup IF gain problem if there FMPP supported frequency compensation. As it stands, I am unable to use my RSPdx
with DSD+ because it's off frequency by approximately 300 Hz at 850 MHz that causes decoding errors that results in choppy audio.

It would be nice if the folks at SDRPlay would release a calibration tool similary to Airspy's if the RSPdx has onboard registers that can be set
to make frequency corrections to the TCXO.

I have the same complaint with no facility in FMPA to trim the TCXO along with a couple of other qwirks that I have emailed to the development team that have to date gone unanswered.

Very frustrating!
 
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