Discrepancies in the calculation of satellite passes

[SP6VWN]

Hello,
I noticed in my Retevis RT3S a large discrepancy in the calculated satellite flight times in relation to the actual location of e.g. the ISS station or the Heavens-Above program. The differences are significant and for individual flights they amount to over 20 minutes. I have entered the coordinates, time zone, time and date correctly. I checked it many times. I downloaded the current data on satellite flights but it doesn't change anything.
I don't know what the reason for such a drastic difference is. Maybe someone has already had a similar problem?

[VK3KYY]

Hello,
I noticed in my Retevis RT3S a large discrepancy in the calculated satellite flight times in relation to the actual location of e.g. the ISS station or the Heavens-Above program. The differences are significant and for individual flights they amount to over 20 minutes. I have entered the coordinates, time zone, time and date correctly. I checked it many times. I downloaded the current data on satellite flights but it doesn't change anything.
I don't know what the reason for such a drastic difference is. Maybe someone has already had a similar problem?

This is really a question for a decicated AMSAT forum.

The prediction algorithm has not changed in the last 2 years and is accurate to a few seconds.

But, the prediction is only as good as the "Keps" data.

The ISS often changes its orbit to avoid debris, and not all datasets get immediately updated

You can choose the URL from where the CPS gets its data.

Try a different dataset URL.

Also did you confirm the accuracy of the Heavens-above predictions?

[SP6VWN]

You're talking about an accuracy of up to a few seconds, but I'm talking about a delay of more than twenty minutes. A few seconds would be ok in this case.
What other sources can I download Keps data from?
Is it possible that despite downloading data, I still have old "Keps" data on the radio?
I have confirmed this with other sources and they are consistent. Only my RT3S gives the flight more than 20 minutes in advance.

[F1RMB]

Does your location defined in your transceiver is correct ?

[SP6VWN]

I provided the location for QTH locator JO71SG. I guess I couldn't have made a mistake.

Data for the ISS from two sources. Why don't they converge?

https://celestrak.org/NORAD/elements/amateur.txt:
ISS (ZARYA)
1 25544U 98067A 24007.20598554 .00207552 00000+0 35328-2 0 9994
2 25544 51.6389 37.9443 0003979 3.1041 81.0682 15.50129671433430


https://www.amsat.org/amsat/ftp/keps/cu ... sabare.txt
ISS
1 25544U 98067A 24006.56404657 .00018207 00000-0 32478-3 0 9994
2 25544 51.6420 41.1204 0003425 2.1882 97.3277 15.50126556433334

[VK3KYY]

I provided the location for QTH locator JO71SG. I guess I couldn't have made a mistake.

Data for the ISS from two sources. Why don't they converge?

https://celestrak.org/NORAD/elements/amateur.txt:
ISS (ZARYA)
1 25544U 98067A 24007.20598554 .00207552 00000+0 35328-2 0 9994
2 25544 51.6389 37.9443 0003979 3.1041 81.0682 15.50129671433430


https://www.amsat.org/amsat/ftp/keps/cu ... sabare.txt
ISS
1 25544U 98067A 24006.56404657 .00018207 00000-0 32478-3 0 9994
2 25544 51.6420 41.1204 0003425 2.1882 97.3277 15.50126556433334

These are questions for an AMSAT specific forum. Not here

Thread will be locked as it is not related to the firmware