Re: [Discuss-gnuradio] Anyone have any success getting Pluto to work with WBFM?

[Ed Troy]

Hi,
Thanks for the file! I am beginning to think that I have something wrong with my Pluto since that does not work, either. I just get noise out. I am going to try it on another pc later. I am running Ubuntu 17.04 under VMWare since I don't really have any dedicated Linux machines. But, it should work. I was able to get an RTL to "sort of" work a while ago, although the audio quality was very poor with a lot of noise and breakup.
Regards,
Ed

On 12/18/2017 3:07 PM, Kyeong Su Shin wrote:

Dear Ed Troy:

Update: I was able to reproduce (..or maybe create a similar) problem on an another computer; the problem was mainly due to buffer underrun (may have to do with the data rate of the PlutoSDR source) . The two-clock problem may also exist (but is not tested). There should be a better fix, but as a quick & dirty fix, I just added a few delay blocks to the flowgraph and it worked on that computer as well.

The flowgraph is attached. (Again, it is not a proper fix. Maybe you want to look at better implementations, such as gqrx, or find more appropriate ways to adjust the buffer..)

Regards,

Kyeong Su Shin

On Mon, Dec 18, 2017 at 1:41 AM, Kyeong Su Shin <address@hidden> wrote:

Dear Ed Troy:

(Also, it is not a simple flowgraph, but I heard that there is a test build of GQRX for PlutoSDR (gr-iio based). You should be able to use that to demodulate WBFM signals, if that is all you want..)

Regards,

Kyeong Su Shin

On Mon, Dec 18, 2017 at 1:34 AM, Kyeong Su Shin <address@hidden> wrote:

Dear Ed Troy:

Actually, I did re-test this with a PlutoSDR (I do have one unit at home, although I do not usually carry this with me) and your flowgraph worked on my PC + PlutoSDR once I reduced the sampling rate from 5MS/s to 2.5MS/s (and adjusted the decim ratio accordingly). Could you try different FM stations, different antennas, or different GNU Radio installations (maybe try running this on different computers)?

One other thing that I would check is the sampling rate that the audio card supports. I know 96kS/s is usually an acceptable value (and did work on my PC), but maybe you should try 48kS/s instead.

I am also concerned about the two-clock problem between the PC and the radio, but I still expect to get some audible sounds even in the worst case scenario...

Regards,

Kyeong Su Shin

On Sun, Dec 17, 2017 at 9:08 AM, Ed Troy <address@hidden> wrote:

Hi Kyeong,
First, sorry about the double transmission of my message. I did not attach [discuss-gnuradio] to the first one and when I did not see it, I figured it got lost and so resent with the correct subject line.

I have checked my board and it does seem to work down to 90 MHz. I need to run more detailed tests with a signal generator to get exact sensitivity numbers, but it should be good enough.

I tried making the changes to sample rate and other things that you suggested, but it still does not demodulate FM broadcast signals. I have to admit that the RTL-SDR devices never did a very good job, either, but I attributed that to relatively poor sensitivity, although I have some pretty good ones, as far as they go. I also tried to lower the gain, but that did not seem to work, either.

If anyone has had success getting the Pluto to work with FM broadcast signals, perhaps they could publish the grc file?
Regards,
Ed

On 12/15/2017 8:33 PM, Kyeong Su Shin wrote:

Dear Ed Troy:

I don't have the PlutoSDR with me right now, so I cannot test it now, but a few things to check:

-Make sure that your Pluto can go down to 90MHz alright; it is only rated to operate on 325MHz - 3.8GHz, and not guaranteed to behave well on such frequencies (even when you did made the changes).

-Try lower sampling rate; like 2MS/s. PlutoSDR is known to drop samples at relatively high sampling rates (and yes, I do mean that 5MS/s is too high).

-Try lowering gain; FM signals can easily overload the frontend of such devices.

If I replace that PlutoSDR source block with an Osmocom source block, change the carrier frequency to my local station, and attach a different radio, it works. (Can't test on a PlutoSDR now, as I do not have one with me now).

Regards,

Kyeong Su Shin

On Fri, Dec 15, 2017 at 4:12 PM, Ed Troy <address@hidden> wrote:

Hi,

I have been trying to get my Pluto to work with WBFM, but I am not having any luck. I am attaching a grc file that I am pretty sure should work, but it does not. It just generates sporadic noise. I did the changes recommended to get the Pluto to work over a wider frequency range, and the results indicated that the changes worked. And, I have tried using the Pluto at higher frequencies to detect a WBFM signal, and it still does not work properly. So, I know it has to be something with my grc file.

What am I doing wrong?

Ed



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