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Re: communication of two b200 via ax.25

From: bryan
Subject: Re: communication of two b200 via ax.25
Date: Thu, 24 Jun 2021 20:39:01 +0900

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*

On Thu, Jun 24, 2021 at 4:58 PM Fabian Schwartau <fabian@opencode.eu> 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,

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

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