How do I calculate losses on a coax cable if I have the input voltage and the reduced output at a different phase angle? The cable length is 100m.
If you are trying to measure Coax loss, then you need to look at it differently than simple resistance.
Coax has a certain dB loss per unit of measure (feet, meters) at a given frequency. So, you need to look up the loss at your operational frequency and calculate the attenuation for 100 Meters. There are dozens of coaxial cable types, so you need to look at the markings on the cable you are using. Next you need to look up the loss characteristics of that cable. That is about 90% of the work.
After you know how many dB loss you have in the cable, you also need to add in the loss of the connectors at each end of the cable. Usually this is a dB or two per connector, depending on frequency.
Next, you need to factor in any other losses between your RF source and the load.
Next you need to factor in the impedance match between the source and the load. Do you have a high Voltage-Standing-Wave-Ratio (VSWR)?
Phase shift is *usually* not important unless you are connecting to multiple antennas or are concerned about arrival time over multiple circuits.
In short, it is a bit more complicated than you think.
