Antenna Testing thresholds
Antenna Testing thresholds
(OP)
Does anyone have some concrete benchmarks for antenna/cabling testing? I am looking for minimum acceptable levels for the following : Return Loss (in dB)
VSWR
cable loss (dB/m , dB/ft)
Basically I looking for general bencha=marks...values that should make me go "what's wrong here!" Thanks in advance
VSWR
cable loss (dB/m , dB/ft)
Basically I looking for general bencha=marks...values that should make me go "what's wrong here!" Thanks in advance





RE: Antenna Testing thresholds
VSWR - normally as 'bad' as 2:1 is considered acceptable for most non-critical communications work. Less critical applications might even accept 3:1, but maybe try to fix it when they had time. There are MANY applications where 2:1 would NOT be acceptable (one example: high power radar where high VSWR would cause arcing in the waveguide). Certain antennas can have extreme VSWR on certain parts of the feedline (as a matching system).
Return Loss is the same thing as VSWR but on a different scale. You can look up the conversion tables.
Cable Loss goes up with frequency. Most HF cables might have one or a couple of dB per hundred feet. Good TV coax can be several dB per 100' even at 1 GHz. To know the limits for a certain cable, you need to know the frequency and simply look it up in the specs for that exact cable.
The above is the short answer.
The longer and more accurate answer is: 'It depends...'
RE: Antenna Testing thresholds
Rtn loss for each connector of a cable should be -25 dB as good, -20 dB as mediocre, and -17 dB as unacceptable for an sma connector at Ku band (12-18 ghz). That's using time domain measured for each connector.
Typically, overall return loss of a good cable is -30 dB in the 200 Mhz range (-34 to -38 dB measured on 0.25 inch semi-rigid cable recently with two type N connectors), and closer to -20 dB at 18 ghz.
0.141" semi-rigid cable loss is typically 0.6 dB/foot at 18 ghz, good expensive ($600 for a 4 footer) cable is 0.25 dB/foot at 18 ghz. Loss is proportional to sqrt of frequency, so at 4.5 ghz, loss is about half that amount.
check out Storm cable or other cable manufacturers, they have alot of spec's for VSWR and loss.
kch
RE: Antenna Testing thresholds
RE: Antenna Testing thresholds
kch