Ongoing audio woes with DSDPlus/FastLane

[KG4LBJ]

I’ve been using DSDplus/FastLane for about 5 months and have always had a problem “decoding” the audio from two local P-25 federal systems. I am using the RTL-SDR USB dongle. Otherwise, DSDplus/FL does a good job of capturing P-25 radio IDs. Also, other modulation protocols (non P-25) from other systems decode nicely.

In fact, my Radio Shack Pro96 with stock antenna receives these two systems just fine – no problems regarding garbled/distorted voice comms so encryption is NOT the issue. (BTW, one system operates at 166.xxx MHz and the other at 419.xxx MHz.) I had hoped that nearby commercial FM station was the problem, but the addition of an FM filter shows no improvement.

I have attempted to improve the output by following the directions regarding advanced decoder options. (Thanks to ALL who helped me in a prior thread regarding this.) But my applied corrections have not shown any improvements – voice still is garbled/trashy.

(I have attached a zipped XLS file showing the maxima of the three parameters, ds, dd, and dv. AND, have also included the raw output WAV file.)

Hoping that a more experienced use could take the time to examine/decode my enclosed sample raw input WAV file and let me know their opinions regarding the source of my audio quality problem.

 

[slicerwizard]

Your raw audio is full of discontinuities and the symbol centering display in the DSD+ console window title is jumping around like a crack addict. I'd guess this is likely caused by lost I/Q samples. If you're using FMP24, try the lost I/Q data test (press the L key in FMP24)

 

[KG4LBJ]

SW, thanks for showing me the centering display. I had never noticed it before. (Although I'm not sure what I'll do with this new found knowledge.. LOL)

But seriously you've lost me with the "L" key thingy. I can't find any reference to it within the help file. (Yes, I've learned my lesson regarding "up to date" documentation.)

(Maybe you meant the "R" key (within FMP24) for I/Q ?? I dunno - I'm not well versed in the finer details, yet.)

Sounds like , if it is losing data in real time, I should try using a different computer..

Thanks again!

 

[a417]

Do some basic testing on your system with rtl_test. if it shows you are routinely dropping samples, it will tell you.

 

[slicerwizard]

C:>FMP24 -h

FMP24 2.70


Usage:
FMP24 [options] Normal operation
FMP24 -h Show help

Options:
-i0 Use first available RTL SDR device [-i0]
-i<num> Use RTL SDR device specified by <num> (1-255)
-i"<ser>" Use RTL SDR device with specified serial number string
-o<num> Output audio device (1-255) [-o1]
-o<linkID> Output audio DSD+ Link ID (256-65535)
-oT<port> Output audio TCP port (256-65535)
-g<num> RF gain (dB) [max]
-T<num> Enable/disable bias tee (0-1) [-T0]
-P<num> Frequency correction PPM value (-999.9-999.9) [-P0.0]
-a<num> Enable/disable auto center tuning (0-1) [-a1]
-q<num> Enable/disable squelch logic (0-1) [-q0]
-f<MHz> Initial tuned frequency [-f99.9]
-b<kHz> Initial RF filter bandwidth (4, 7, 9.5, 12.5, 22) [-b7]
-b-<kHz> Set initial RF filter bandwidth and ignore hints from DSD+
-t<num> Initial RF filter set (standard or tight) [-t0]
-u<num> Enable/disable unlicensed spectrum display (0-1) [-u0]
-z<num> Show zoomed spectrum (0-1) [-z1]
-n<num> Select noise filter (0-2) [-n0]
-v<num> Set volume level (0-500) [-v100]
-s<num> Enable/disable scanner mode (0-1) [-s0]
-y<num> Select spectrum survey list file (0-999) [-y0]
-wsl<v>.<h> Spectrum window location [-wsl50.50]
-_<num> Minimize windows at startup; bitmapped
-rc Role is trunk control/rest channel monitor
-rv Role is trunk voice channel monitor

Active keys:
0-9 . Enter set frequency
[/] select step size
Cursor </> step frequency
Ctrl Csr </> step frequency by 250 Hz

A toggle auto center tuning
D cycle audio demodulation mode
Q toggle squelch mode
U toggle unlicensed spectrum display mode
M toggle spectrum memory overlay
X reset spectrum memory
Z toggle spectrum zoom overlay
I select injection mode
b/B select RF bandpass filter
T select tight or standard RF bandpass filter set
t enable/disable bias tee
N select noise filter
L toggle lost I/Q data test mode
Cursor ^/v adjust volume level
spacebar toggle muting

g/G adjust RF gain
p/P adjust PPM frequency correction

R toggle raw I/Q and FM demod recording

S start scanner mode or exit hold mode
Y start spectrum survey
C start trunk control/rest channel following mode
V start trunk voice channel following mode

? list active keys
Esc exit scanner/survey/CC/VC modes or exit program

Left click on spectrum: retune


Notes.txt:

FMP24 2.70

Added direct connection mode:

Connects DSD+ to FMPA/FMPP/FMP24 without using network.

Use -o<linkID> on FMPA/FMPP/FMP24 command line for direct connection.

Use -oT<addrort> on FMPA/FMPP/FMP24 command line for TCP link to remote PC.

Added I/Q data loss diagnostic mode; Press L key to start/stop data loss test.

Added DLL files integrity checks. Required DLLs must be present in FMP24's working folder.
Missing DLLs can be acquired via the DSD+ Download Newest Base Files menu entry.

 

[a417]

...time to upgrade to 2.70!

 

[KG4LBJ]

Dohhh, hold on while I extricate my foot from my mouth!! Guess my annual subscription has expired?

I seem to be running version 2.275. Assumed that when I checked for updates via the MISC menu it would have indicated I was behind the times instead of telling me I was running the most recent version.

Sounds like I need to send somebody $25.

 

[KG4LBJ]

Once again, some supporting details.... Turns out I am using FMP24 ver 2.65 and DSD+ ver 2.275.

Don't know how I missed any updates as I still have 5 months remaining in my annual subscription.

 

[slicerwizard]

Use DSD+ to download the base files. An up to date FMP24 (and everything else) will be in there.

You should be able to copy all exe and dll files to your DSD+ folder without creating any problems.

 

[msingewald]

I am using FMPA with an Airspy, and it looks like l/L controls VGA gain. Does this function use a different key with FMPA or does it not exist for this device?

C:>FMP24 -h

FMP24 2.70


Usage:
FMP24 [options] Normal operation
FMP24 -h Show help

Options:
-i0 Use first available RTL SDR device [-i0]
-i<num> Use RTL SDR device specified by <num> (1-255)
-i"<ser>" Use RTL SDR device with specified serial number string
-o<num> Output audio device (1-255) [-o1]
-o<linkID> Output audio DSD+ Link ID (256-65535)
-oT<port> Output audio TCP port (256-65535)
-g<num> RF gain (dB) [max]
-T<num> Enable/disable bias tee (0-1) [-T0]
-P<num> Frequency correction PPM value (-999.9-999.9) [-P0.0]
-a<num> Enable/disable auto center tuning (0-1) [-a1]
-q<num> Enable/disable squelch logic (0-1) [-q0]
-f<MHz> Initial tuned frequency [-f99.9]
-b<kHz> Initial RF filter bandwidth (4, 7, 9.5, 12.5, 22) [-b7]
-b-<kHz> Set initial RF filter bandwidth and ignore hints from DSD+
-t<num> Initial RF filter set (standard or tight) [-t0]
-u<num> Enable/disable unlicensed spectrum display (0-1) [-u0]
-z<num> Show zoomed spectrum (0-1) [-z1]
-n<num> Select noise filter (0-2) [-n0]
-v<num> Set volume level (0-500) [-v100]
-s<num> Enable/disable scanner mode (0-1) [-s0]
-y<num> Select spectrum survey list file (0-999) [-y0]
-wsl<v>.<h> Spectrum window location [-wsl50.50]
-_<num> Minimize windows at startup; bitmapped
-rc Role is trunk control/rest channel monitor
-rv Role is trunk voice channel monitor

Active keys:
0-9 . Enter set frequency
[/] select step size
Cursor </> step frequency
Ctrl Csr </> step frequency by 250 Hz

A toggle auto center tuning
D cycle audio demodulation mode
Q toggle squelch mode
U toggle unlicensed spectrum display mode
M toggle spectrum memory overlay
X reset spectrum memory
Z toggle spectrum zoom overlay
I select injection mode
b/B select RF bandpass filter
T select tight or standard RF bandpass filter set
t enable/disable bias tee
N select noise filter
L toggle lost I/Q data test mode
Cursor ^/v adjust volume level
spacebar toggle muting

g/G adjust RF gain
p/P adjust PPM frequency correction

R toggle raw I/Q and FM demod recording

S start scanner mode or exit hold mode
Y start spectrum survey
C start trunk control/rest channel following mode
V start trunk voice channel following mode

? list active keys
Esc exit scanner/survey/CC/VC modes or exit program

Left click on spectrum: retune


Notes.txt:

FMP24 2.70

Added direct connection mode:

Connects DSD+ to FMPA/FMPP/FMP24 without using network.

Use -o<linkID> on FMPA/FMPP/FMP24 command line for direct connection.

Use -oT<addrort> on FMPA/FMPP/FMP24 command line for TCP link to remote PC.

Added I/Q data loss diagnostic mode; Press L key to start/stop data loss test.

Added DLL files integrity checks. Required DLLs must be present in FMP24's working folder.
Missing DLLs can be acquired via the DSD+ Download Newest Base Files menu entry.

 

[Forts]

Maybe try fmpa -h and see what it spits out?

 

[msingewald]

I believe -h would be a startup switch, but I did try just h while it was running and there was no response.

Maybe try fmpa -h and see what it spits out?

 

[BM82557]

This works for me --

Start CMD /c "DSDPlus -h > DSDPlus_Help.txt"
Start CMD /c "FMPA -h > FMPA_Help.txt"
Start CMD /c "FMP24 -h > FMP24_Help.txt"

 

[phyberoptics]

Great that the instruction is in the help file, but is there anything anywhere to outline how that function works? LOL

 

[BM82557]

Forgot to mention that the following is in a batch file that I setup to create the respective Help files --

Start CMD /c "DSDPlus -h > DSDPlus_Help.txt"
Start CMD /c "FMPA -h > FMPA_Help.txt"
Start CMD /c "FMP24 -h > FMP24_Help.txt"

 

[msingewald]

That lists the commands, and there is no LOSS MODE commands for the FMPA for Airspy. I already knew that, but that is a helpful way to get those in a text file.

This works for me --

Start CMD /c "DSDPlus -h > DSDPlus_Help.txt"
Start CMD /c "FMPA -h > FMPA_Help.txt"
Start CMD /c "FMP24 -h > FMP24_Help.txt"

 

[KG4LBJ]

An odd resolution (?) to my issues follows, but first, Thanks to slicerwizard and a417 for helpful info!

This problem has been really bugging me for the past few months as occasionally I would receive clear/ungarbled voice comms but not often enough to see any pattern to the problem.

(Finally took my own advice and tried another computer this week, LOL - What a difference that made!)

As mentioned in another thread, I live near a commercial FM transmitter site and decided to try an "FM filter." On my original laptop computer (a "fast" ASUS with Intel i7 cpu with 16 GB of ram) the filter blocked all FM stations EXCEPT for the nearby station. On my older substitute laptop computer (an extremely "slow" HP with an AMD A8 cpu and 8 GB ram) the same filter blocked ALL FM stations.

Perhaps the HP has better shielding because suddenly I was routinely receiving clear voices. So, mystery solved? (I think so but next week when I have time I'll try the substitute computer without the filter and see if I have the same symptoms.)

 

[KG4LBJ]

Just to wrap up my initial questions for this thread:

The HP laptop continued to give acceptable results without the FM filter but it was not quite as good as having the filter installed. So my SWAG (scientific wild assed guess) is that close proximity to a commercial FM site is not a good thing. (Also, I believe that the "shielding" of the Asus is inferior to the HP but I have no way of conclusively proving this, i.e. I don't intend to start a dog fight over the merits of two different computer companies!)