For an upload the spacecraft remembers how far you got through the upload process.  It stores the file offset for the last byte that it received.  When you login and request to upload of the same file on the next pass it tells you the offset number to start from.  The ground station software should then begin uploading from that point.  So in theory it should complete over several passes as needed.

One common issue is having too much uplink power so that you can't receive while uplinking.  The full duplex nature of the channel means that you need to be able to receive responses from the spacecraft when your receiver might be desensitized.  So make sure either your antennae are isolated enough or you are not using too much power.  10 -25 watts should be sufficient into a yagi.

But tell us a bit more about the setup you are using,  Which software, tnc, radio, antenna and we can try to help.



On Fri, Mar 26, 2021 at 2:35 PM <> wrote:
I've successfully been working the Falconsat-3 PBBS, downloading files and uploading text messages. However, when I try to upload a bigger file, like an image, I can't get it to complete even across a number of passes. I've been trying to upload a 20 kB jpeg, but the most I can get uploaded is around 18%. Some passes it doesn't start to upload anything, even though I'm capturing other data coming down and it acknowledges my callsign on the system. After a few unsuccessful passes, it starts to upload again from 0%.

I'm trying to figure out which part of the link is the problem. I switch from my TH-D72 to my TM-V710 so that the uplink is 50W, so maybe my downlink is not consistent enough to hold the connection? My UHF side is only 5 elements, so maybe not as much gain as others are using.

Does it restart the upload from scratch because of how the satellite software is written or is it something with the ground station software?

Any advice would be appreciated.



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Chris E. Thompson