Observation 749523: CZ-4B R/B (43656)

Hello all,
is this signal is correct ?
F6HDW Jean Claude


This is a terrestrial signal. Except that it isn’t a straight line, as it should, also it doesn’t look like the rest of the good observations.

Thank Fredy
ok I understand only a straight line is a good signal.
F6HDW Jean Claude

Exactly, except in some cases:

  1. The satellite has old TLE. TLE is a calculation of orbit parameters in a certain time and describe the orbit a “little” before and a “little” after that certain time. How much will be this “little” depends on several parameters, like the current orbit. It could be from 6-7 weeks to a day or couple of hours.

  2. The newly deployed satellites that haven’t assigned a norad id. This is similar to the above, meaning that without accurate TLEs we can not calculate the orbit right. What happens is that we use TLE from objects in the same deployment, which are not 100% accurate.

  3. Satellite transmitter is faulty or is affected by its power supply. There are cases where the transmitter doesn’t transmit steadily on its announced frequency.

I think these are the cases we have met signal that it isn’t in a straight line on waterfall.

Here is a great example of a “good” observation, but the signal is not straight because of slightly outdated TLE: