trouble-shooting timing jump issue with RSP1A on Raspberry Pi

[scottlirwinParticipant]

Hi all,

I am new to your group and hoping someone can help me trouble-shoot a timing jump issue on my Raspberry Pi. A similar problem with no solution was posted here.

BACKGROUND
I use a Raspberry Pi 4 with 4 gigs of ram as a self-contained wefax station while camping in my truck in Baja California. The Pi is running Raspbian GNU/Linex 10 (buster) and is built off of the original image I downloaded from SDRPlay website (SDRplay_RPi_V0.6.img.xz). I use a RSP1A to receive wefax images from the U.S. Coast Guard station in Pt. Reyes, California. I use CubicSDR v0.2.5 (on the image referenced above) to manage the radio and Fldigi 4.1.12.12 to decode the images.

PROBLEM
Once in awhile a recorded image will contain a “jump”. See attached as an example.

At first I thought the problem was related to Fldigi itself. I was working with David, the author of Fldigi, to address this issue (as well as another unrelated one). Follow this link to view a post from the groups.io for the Fldigi app for info on this discussion.

I now think the problem may be related to either CubicSDR or the RSP1A radio itself. I came to this conclusion because when I used Fldigi to record the audio of a transmission that contained a jump, then used Fldigi to decode from the recording, I could replicate the jump every time in the exact same place even when CubicSDR wasn’t running on my Pi. Follow this link to download a copy of the file. You will need to wait a few seconds for the actual transmission to start. David attempted to decode my recording and experienced the same issue as well. He referred to it as a “timing jump during reception”. Another member of the group named Brian said he experiences the issue when using an RSPduo to receive images but that he did NOT experience the problem when he used an IC-7300.

QUESTION
Has anyone in this group ever experienced this problem on a Pi while using an RSP1A and are there any suggestions for what I can do to resolve this?

Thanks for any help you can provide.

Scott
KJ6MWX

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