Iridium Modem to Antenna: Measuring vs Calculating dB Loss at 1626.4MHz in 9m Coax

So I’ve tried to calculate and test the loss in dB at a specific frequency in a coaxial cable. I want to know the theoretical max length of a cable which will be connecting an Iridium modem to an antenna.
I’ve calculated the loss in dB using the following method:
https://www.meinbergglobal.com/english/specs/gpscable.htm

Results can be found in the attacthed PDF.

To validate my calculations, I wanted to test the loss in dB in the real world using a spectrum analyzer, a function generator and the specified cable with a length of 9m.

The two pictures show the setup of the function generator and the reading from the spectrum analyzer.

The reading from the spectrum analyzer shows that at at frequency of 1626.4MHz the signal has a strength of -17.0 dBm. While the output from the function generator is -10.0 dbm.
Calculating the power ratio in dB between the two, gives a loss of 2,3 dB.

In the theoretical calculations I expected a loss of around 1.674 dB when using this specific 9m cable.

Can someone explain to me what I’m doing wrong, are my calculations flawed or does the plug converters between the cable and the instruments (in both ends) introduce an extra loss. I feel like I’m a bit to much off between the real world test and the theoretical calculations.

A loss in connectors is to be expected. You mention plug converters at both ends - are these just plugs (eg BNC) or converters (eg BNC to SMA or N type connectors?

Various estimates I found on the net very from 0.1 dB for a really good connector to 0.5 to 1 dB which you would probably experience for adapters and other connectors. So with 2 connectors / adapters, a loss of around 0.6 dB is not soo bad.

You could try your measurements with a longer length of the same coax and see what the discrepancy is. If you still get the same difference between your predicted and actual readings it is almost certainly connectors.

https://www.quora.com/Do-coaxial-couplers-reduce-signals

It's not uncommon for connectors to cause some loss of signal strength when transmitting a signal through a coaxial cable. The amount of loss can vary significantly depending on the type of connectors being used and their quality. For example, high-quality connectors may have a loss of around 0.1 dB, while low-quality connectors or adapters may have a loss of 0.5 to 1 dB or more. If you're using plug converters at both ends of the cable, it's important to make sure that they are of good quality to minimize loss.

If you're experiencing a discrepancy between your predicted and actual readings when transmitting a signal through a coaxial cable, it's possible that the connectors are contributing to the loss. To determine whether this is the case, you could try measuring the signal strength with a longer length of the same coaxial cable and see if the difference between your predicted and actual readings remains constant. If it does, it's likely that the connectors are the cause of the loss. On the other hand, if the difference changes as the length of the cable changes, it could be due to other factors such as the type of coaxial cable being used or the frequency of the signal.