Re: Message Strobe and SDR problem

Hi Marcus and Adrian,

Apologies for the incorrect link to the private image. You are correct, the diagram in the README.md is the proper one. Thanks a lot for your advice.

For now, I've tried the simplest solution — adding a "Simple Squelch" block to feed the "Polyphase Clock Sync" only when a signal is present. The updated schematic is now available in the README.md of the project on GitHub:
https://github.com/yabool2001/BPSK_test_02_3

Unfortunately, it didn't help. In this configuration, the project only works with a continuous source, such as "Constant Source". If there is a better implementation for signal detection that could assist in burst transmission, I'd be grateful for your recommendation.

Now, I will also try Adrian's suggestion to implement the "Correlation Estimator" block.

Thanks again for your support!

Best regards,
Yabool2001

pon., 12 maj 2025 o 14:51 Marcus Müller <mmueller@gnuradio.org> napisał(a):

Hi Maciej,

sadly, you attached a link to a picture on
https://private-user-images.githubusercontent.com… , which is github-account-specific and
can't be used by anyone but you. But the raw URL in your Readme works,
https://github.com/user-attachments/assets/3f9eee70-811e-41be-9d43-877b2dcbb078
so I'm assuming that's the one.

What I think is wrong here is that the Polyphase Clock Sync drifts off during the pauses
between frames: it doesn't know whether it's looking at noise only or signal, and so tries
to "wildly" guess what it should do during the "noise only" periods, just to then be off
from the correct timing enough to not be able to catch up with it during the first few
symbols of each frame.

In a practical system, you'd need to first detect presence before you feed it through the
clock synchronizer.

Best regards,
Marcus

On 5/12/25 10:47 AM, Maciej Zemło wrote:
> Hi everyone,
>
> I've developed a brief demonstration project in GRC that transmits a single byte via Pluto
> using BPSK modulation. The project works well when using a "Constant Source" block that
> continuously sends the byte, but it completely fails to function with the "Message Strobe"
> block, which sends a byte every 0.5 seconds.
>
> The project is available on GitHub for further reference: https://github.com/yabool2001/
> BPSK_test_02_3 <https://github.com/yabool2001/BPSK_test_02_3>
>
>    I've attached a screenshot illustrating the structure of the project, available here
> <https://private-user-
> images.githubusercontent.com/38382353/442661233-3f9eee70-811e-41be-9d43-877b2dcbb078.png?
> jwt=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.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.whxllXKHs55LV7wgcRfq7BPy3oQjAiGJWUoKc-J8en8>.
>
> Could someone point me in the right direction regarding what might be going wrong here?
>
> Thanks in advance for your assistance!
>
> Best regards,
> Yabool2001
>