SDR# [Help Needed] Using SDR# for Loading and Decoding POCSAG IQ Signals from Hard Drive

TurboT92

Member
Joined
Dec 12, 2023
Messages
5
Hey guys,

a colleague of mine needs to use SDR# to decode POCSAG signals stored on his hard drive.

Following problems have I found:

1) As far as I found out now, the only way to load files from the hard drive is by using the Baseband File Player. I doubt that any of the example files (e.g. the ones from POCSAG - Signal Identification Wiki when converted from mp3 to wav) he got are in the Baseband frequency. I think this might be issue #1.

2) When playing those files, nothing occurs in the POCSAG Decoder list (should be not the case if issue #1 would not be an issue at the first place).

Did anyone of you do anything similar to this and might have a solution? It is time critical so any fast help is very appreciated! <3

SDR# Version: v1.0.0.1919
POCSAG Decoder Version: r5 from April 20th, 2021
 

thewraith2008

Member
Joined
Nov 22, 2016
Messages
1,884
Your source files cannot be saved/stored in a compressed format (e.g. MP3).
If they are, then they will not work. (signal has been distorted by the lossy compression).

Also the recordings POCSAG signals must be done with a discriminator tap or some IF recorder that does not have any DSP filtering.

The file input frontends of SDR# need the data to be stored as interleave IQ data (in a WAV container).
SDR# input via soundcard also requires the IQ data as above.

I don't think you can use demodulated signal (WAV) as a source for SDR#.

You may want to try PDW software and you should be able to pipe your WAV files audio in to PDW (so long as they are suitable).
 

TurboT92

Member
Joined
Dec 12, 2023
Messages
5
Thanks for your help and answer!

Your source files cannot be saved/stored in a compressed format (e.g. MP3).
If they are, then they will not work. (signal has been distorted by the lossy compression).

Also the recordings POCSAG signals must be done with a discriminator tap or some IF recorder that does not have any DSP filtering.
Regarding MP3 compression: Alright, I did not think that that might be such an issue.

Regarding well recorded POCSAG signals: Do you know by chance where to find such signals online? Maybe you do have some on your PC somehow? Since I do not have any antenna or receiving device, I can not record them by myself...

The file input frontends of SDR# need the data to be stored as interleave IQ data (in a WAV container).
Any chance to maybe create such an file via Audacity or similar softwares?

You may want to try PDW software and you should be able to pipe your WAV files audio in to PDW (so long as they are suitable).
Unfortunately I have to use SDR#. Or do you mean I could use PDW to load the existing files and use PDW to make them suitable for SDR#?
 

thewraith2008

Member
Joined
Nov 22, 2016
Messages
1,884
Regarding well recorded POCSAG signals: Do you know by chance where to find such signals online? Maybe you do have some on your PC somehow? Since I do not have any antenna or receiving device, I can not record them by myself...
You could try the SDR# Spy Server front-end, I can't point to a specfic online SDR for POCSAG signals as you generally need to look and see for yourself if they are present.

No I don't have files to make available. I've not played with POCSAG for sometime. (I think the local ones got shutdown because of irresponsible peanuts).

Any chance to maybe create such an file via Audacity or similar softwares?
You can do this with SDR# plug-ins like 'IF Recorder' to create IQ files or possibly use 'Audio Recorder' to only record the demodulated output.
1st option can be played back with the SDR# 'File Player' plug-in. (and use it with the SDR# POCSAG Decoder plug-in)
With the 2nd option and any demodulator output audio files you already have, you could play them back with Audacity and pipe to PDW to decode the messages. (But not back into SDR# and have it processed by POCSAG Decoder plug-in.)

Unfortunately I have to use SDR#.
Why limit yourself?

Or do you mean I could use PDW to load the existing files and use PDW to make them suitable for SDR#?
No.
Play any demodulator output audio files you already have (or record) back with Audacity and pipe to PDW so it will decode the messages.

This is the nature of SDR sometimes, to use more than one program to achieve a desired outcome.
 

LimaZulu

Member
Joined
Jul 7, 2011
Messages
379
A simple solution could be to use any audio software and virtual cable. Let's say you use vlc. Put virtual cable 1 as output device in vlc, load your wav sample then on sdr# select virtual cable 1 as input. Simple as that and could be done with any other wav player as well.
Btw whats the need of SDR#? As already been said, pdw is the software for such task and could be directly fed by the above mentioned way. In short vlc->virtual cable->pdw.
 

thewraith2008

Member
Joined
Nov 22, 2016
Messages
1,884
A simple solution could be to use any audio software and virtual cable. Let's say you use vlc. Put virtual cable 1 as output device in vlc, load your wav sample then on sdr# select virtual cable 1 as input.
The SDR# input is only enable using the front-end 'IQ from Sound Card'.
This input requires the audio stream from sound card (or virtual cable) to be interleaved IQ data and at the selected samplerate.
SDR# can't render a correct FFT frequency spectrum (and other things) just using demodulated output audio file as input source.
 

dlwtrunked

Member
Premium Subscriber
Joined
Dec 19, 2002
Messages
2,434
You could try the SDR# Spy Server front-end, I can't point to a specfic online SDR for POCSAG signals as you generally need to look and see for yourself if they are present.

No I don't have files to make available. I've not played with POCSAG for sometime. (I think the local ones got shutdown because of irresponsible peanuts).


You can do this with SDR# plug-ins like 'IF Recorder' to create IQ files or possibly use 'Audio Recorder' to only record the demodulated output.
1st option can be played back with the SDR# 'File Player' plug-in. (and use it with the SDR# POCSAG Decoder plug-in)
With the 2nd option and any demodulator output audio files you already have, you could play them back with Audacity and pipe to PDW to decode the messages. (But not back into SDR# and have it processed by POCSAG Decoder plug-in.)


Why limit yourself?


No.
Play any demodulator output audio files you already have (or record) back with Audacity and pipe to PDW so it will decode the messages.

This is the nature of SDR sometimes, to use more than one program to achieve a desired outcome.

That is the only reasonable way to do this and many do it that way.
 

TurboT92

Member
Joined
Dec 12, 2023
Messages
5
Hi all,
thanks for your help and answers firstly!

Why limit yourself?
Unfortunately my friend's task limits our options. They ask him to do a demo using SDR#. So no PDW for him...but I understand that this would be the 'easier' way to do it.

You could try the SDR# Spy Server front-end, I can't point to a specfic online SDR for POCSAG signals as you generally need to look and see for yourself if they are present.
I will try this at first and try to find a server where we can find some POCSAG signals.

You can do this with SDR# plug-ins like 'IF Recorder' to create IQ files or possibly use 'Audio Recorder' to only record the demodulated output.
1st option can be played back with the SDR# 'File Player' plug-in. (and use it with the SDR# POCSAG Decoder plug-in)
With the 2nd option and any demodulator output audio files you already have, you could play them back with Audacity and pipe to PDW to decode the messages. (But not back into SDR# and have it processed by POCSAG Decoder plug-in.)
I will try this if I fail to find a SpyServer with POCSAG signals on it.
Would it also be possible to use an IF Recorder to record IQ files from today from a SpyServer and load them back into SDR#? From what I understood from your first post @thewraith2008 a proper recorded IQ file (with an IF recorder) can be played back via the Baseband File Player.

Thanks again guys! Will keep you updated <3
 

morfis

Member
Joined
Jan 24, 2004
Messages
1,693
I find this whole question very strange:
Your 'colleague' became your 'friend'.

'They' ask him to do a demo...for what purpose and why with some specfici piece of software not designed to do the task at hand?

His problem is'time critical' yet it's based on recordings YOU found online/are requesting.
He has to use SDR# - why? That software is for controlling SDRs not really for decoding pagers. It's probably not the best software for controlling SDRs and the available POCSAG plugin is VERY limited.
Why hasn't your 'colleague'/'friend' created an account on here to ask the questions?
 

TurboT92

Member
Joined
Dec 12, 2023
Messages
5
I find this whole question very strange:
Your 'colleague' became your 'friend'.

'They' ask him to do a demo...for what purpose and why with some specfici piece of software not designed to do the task at hand?

His problem is'time critical' yet it's based on recordings YOU found online/are requesting.
He has to use SDR# - why? That software is for controlling SDRs not really for decoding pagers. It's probably not the best software for controlling SDRs and the available POCSAG plugin is VERY limited.
Why hasn't your 'colleague'/'friend' created an account on here to ask the questions?
Hi, thanks for your answer :)

Sorry for the misunderstandings there. But colleagues can sometimes be friends :) can't they? He has a deadline next week and he is somewhat frustrated since he can not solve it by himself. That's why I decided to help him out in my free time. Regarding the software he has to used: I do not know why they would ask him to do the task using a software not fit for that task. Sorry. I just want to help him out.

I hope that this is a bit clearer now.

If you have some ideas too: that would be awesome!

Also I found a POCSAG IQ Signal, which SDR# SHOULD be able to decode but the Plugin does not do anything unfortunately. Also using the SpyServer I found some POCSAG signals but again: no decoded signals from the plugin... :(
 
Top