Hi Fabian, Thank you so much for your suggestions as well as the advice to try it without the USRPs and escape reality for a bit. Will certainly do that. :-D
Regards, Bryan On Thu, Jun 24, 2021 at 9:03 PM Fabian Schwartau <[email protected]> wrote: > Hi Bryan, > just increase the cutoff of the LPF, not the deviation. I am just saying > that the bandwidth of a signal with 5 kHz deviation is probably more > like 10 kHz wide (single sided). But I am not sure about that. You can > use the "Qt GUI Frequency Sink" to take a look at the spectrum and see > what the bandwidth of the signal is. Just try a few different values and > see if it gets better. > You can also try to put both flow graphs into one and get rid of the > USRPs. Just to make sure that the flow graph alone works as expected > without this annoying thing called "reality" ;) Remember to add a > throttle block. > > Best regards, > Fabian > > > Am 24.06.21 um 13:39 schrieb bryan: > > Hi Fabian, > > Thank you for the reply. Actually, I am just starting to learn the > > ins and outs of GNU Radio and SDR. I will try to increase the cutoff and > > max deviation and check the results. With regards to the Fractional BW > > at TX, I just copied it from some code I found online. Should I change > > it to a different value? *sorry, i am still trying to absorb all the > > concepts* > > > > Regards, > > Bryan > > > > > > On Thu, Jun 24, 2021 at 4:58 PM Fabian Schwartau <[email protected] > > <mailto:[email protected]>> wrote: > > > > Hi Bryan, > > > > I just noticed a few things I am not sure about. Maybe I got > something > > wrong, maybe they are a mistake: > > You transmit at 70cm and receive at 2m. > > You use a low-pass filter with 5kHz cutoff and allow a maximum > deviation > > of 5kHz of the NBFM receiver. I am not sure, but I think this is not > > optimal. I would expect a spectrum quite a bit wider than 5kHz when > > transmitting with 5kHz max deviation. > > Why is the fractional BW of your Rational Resampler in the TX path 0? > > > > Best regards, > > Fabian > > > > Am 24.06.21 um 08:19 schrieb bryan: > > > Hi, > > > I have this flowgraph programmed in two b200 SDRs. I want to > > > communicate via ax.25. The problem is both are not consistent in > > > receiving data from each other. It is like for every 10 > transmitted > > > data, around 5 are received from the other end. Can anybody tell > > me what > > > I did wrong so that the two SDRs will communicate consistently? > Note > > > that both of them are just located very near to each other? Here > is my > > > flowgraph: > > > > > > RX: > > > image.png > > > > > > TX: > > > > > > image.png > > > > > > Regards, > > > Bryan > > > > > >
