Working FM radio on GNU radio and POTHOS

TegwynTwmfatt · 3 April 2017 16:30

Here is my paltry offering - a very simple FM radio with lots of sliders to fiddle about with:

Not the best sound quality, but it works

Any suggestions for improvement welcomed.
.grc file: CLICKY LINKY
Download file and change from .xml to .grc

dpenev · 3 April 2017 20:13

Hi TegwynTwmfatt,

Thanks for sharing.
I can not download the file, permission issue. Anybody succeeded with it?
It is interesting (to me) if equivalent can be made for Pothos.

TegwynTwmfatt · 3 April 2017 20:52

@dpenev I’ll probably replicate it in pothos tomorrow .

martywittrock · 3 April 2017 20:58

@dpenev,

Hover over the ‘CLICKY LINKY’ with your mouse and then do a right click with your mouse to save this file to the desktop and then open it in GNU Radio Companion as appropriate. Should save as FM_RADIO_08.grc

73 de Marty, KN0CK

dpenev · 4 April 2017 06:33

Thanks Marty,

I actually think I should know how to download the file from the Internet after a few decades in front of the computer
but I get 403: Forbidden. Bellow the wget log.

You have managed to get the file, correct?

wget http://www.goatindustries.co.uk/SDR/FM_RADIO_08.grc
–2017-04-04 09:23:30-- http://www.goatindustries.co.uk/SDR/FM_RADIO_08.grc
Resolving www.goatindustries.co.uk (www.goatindustries.co.uk)… 212.113.132.65
Connecting to www.goatindustries.co.uk (www.goatindustries.co.uk)|212.113.132.65|:80… connected.
HTTP request sent, awaiting response… 403 Forbidden
2017-04-04 09:23:30 ERROR 403: Forbidden.

TegwynTwmfatt · 4 April 2017 09:48

sorry @dpenev - I think this website has blacklisted your IP address. Try this instead:

http://www.nanobrewery.co.uk/SDR/FM_RADIO_08.xml

change .xml to .grc.

N1JEZ · 4 April 2017 11:52

Got it running here. I changed it to receive NOAA @ 162.400 NBFM and audio is fine.

Mike

TegwynTwmfatt · 4 April 2017 12:08

@dpenev for Pothos, download this example:

github.com

pothosware/PothosDemos/blob/master/simple_fm_demod/simple_fm_demod.pothos

{
    "globals" : [
        {
            "name" : "deviation",
            "value" : "75000"
        },
        {
            "name" : "sampRate",
            "value" : "1.1025e6"
        },
        {
            "name" : "filterBw",
            "value" : "200e3"
        }
    ],
    "pages" : [
        {
            "graphObjects" : [
                {
                    "blockId" : "Spectrogram0",

This file has been truncated. show original

Best way to do this is to select the ‘Raw’ tab and copy and paste to a .txt on your desk top. I’m using windows 10. Then rename the txt file to a .pothos file. The audio quality is much better than my GNU radio version.

Open the file in pothos and find the ‘Devce Args’ panel and type in: {“driver”:“lime”}. Press ‘Execute’.

The really good thing about Pothos is that it explains everything so is an excellent learning tool.

N1JEZ · 4 April 2017 13:01

I’m having trouble finding the ‘Device Args’ panel…

N1JEZ · 4 April 2017 13:04

Found it. Working here.

Mike

dpenev · 4 April 2017 16:28

Hi @TegwynTwmfatt,

In the GRC I am not able to find the LimeSDR input selection.
Is it fixed to some particular input?
With a portable room antenna I kind of hear something on top of the noise.

hTo137 · 4 April 2017 17:08

Watched this one a while ago and found it useful. I watched it a few times and there were some tidbits that filled in some knowledge gaps for me.

TegwynTwmfatt · 4 April 2017 17:10

It seems to default to RX1_L, so plug the antennae into that socket. You could also try typing RX1_L into the Ch0: Antenna box.

TegwynTwmfatt · 4 April 2017 17:11

I used this video to create the GNU radio sketch!

dpenev · 4 April 2017 22:07

It seems it doesn’t work for me.
…
return _osmosdr_swig.source_sptr_set_antenna(self, antenna, chan)
RuntimeError: SoapyLMS7::setAntenna(RX, RX1_L) - unknown antenna name

But it is clear that RX1_L is used.

TegwynTwmfatt · 5 April 2017 08:34

OK … just leave the box blank and it should default to RX1_L

dpenev · 5 April 2017 08:45

OK the Pothos FM example working also for me. It seems it also defaults to RX1_L and I had to set the Rx Front end Gain to 50.
I will try to spend some time on this framework next few days.

P.S. The digits (on the Pothos widgets) rendering seems to bother my eyes. Anyone having same issue or knowing how to improve? What I have on screen attached,

dpenev · 5 April 2017 08:52

Seems to relate mostly with the case widgets are zoomed.

Ismas · 5 April 2017 12:23

If memory serves, for antenna selection, use “LNAL”, “LNAH” or "LNAW " for source, and “BAND1” or “BAND2” for sink in “Ch0: Antenna”

TegwynTwmfatt · 5 April 2017 17:17

@Ismas I got Pothos to transmit using the SDR sink block with a ‘0’ in the channel box. It transmitted on TX1_1. No antenna info needed