[TowerTalk] Elementary feedline loss question
grants2 at pacbell.net
Fri Apr 4 14:31:02 EDT 2014
Perhaps a less error prone way to measure loss is to use your
transmitter, dummy load, and SWR/power meter. I put the power meter at
the transmitter and set the power level on the SWR meter. Then move it
to the load end and measure again. Then
db loss = 10 log(Pout/Pin)
Your rig is more accurate in freq than the MFJ and the same power meter
and load are used to take out those variables. Also works for freq.
where the MFJ won't go.
I've measured various vintage RG8's 12 to 20 YOA and found near original
spec loss, although some of it was MIL-SPEC quality. I then tape on the
cable the date, measurement freq, and loss for future reference.
On 4/4/2014 6:53 AM, Pete Smith N4ZR wrote:
> If I terminate a long 50-ohm coaxial cable with a 50-ohm dummy load,
> and put an MFJ-259B on the other end, and it reads R=56, X=0 at a
> given frequency, what is the mathematical relationship between the
> measured R (leaving calibration out of it, for now) and the loss in dB?
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