[amsat-bb] Re: Feed Line Loss @ Freq vs. Price

----- Original Message ----- From: "Stargate" stargatesg1@verizon.net To: amsat-bb@amsat.org Sent: Thursday, May 10, 2007 11:26 PM Subject: [amsat-bb] Re: Feed Line Loss @ Freq vs. Price

While on this subject, has anyone used a "Return Loss Bridge" (RLB) to measure their actual total system loss. I was planning on doing that when I get my antenna

system

up and running to give me a base line for future improvements.

Any thoughts?

Thanks. RoD KD0XX

Hi Rod, KD0XX

Disconnect your coax cable from the antenna connector and short circuit the inner conductor with the outer conductor at your transmission line output end.

Then using your RLB measure the Return Loss at the other end of the line near your TX or RX and convert the measured Return Loss in dB to the equivalent SWR

In this conditions the matched-line loss for the frequency of measurement may then be determined from:

Lm (dB) = 10 log [ (SWR+1) / (SWR-1) ] 10

Where SWR = the SWR value measured at the line input with the other end shorted

Example:

If the measured return loss of your short-circuited line is 2.92 dB corresponding to a SWR = 6 then the matched-line loss of your transmission line at the frequency of measurement is Lm = 1.46 dB

Best 73" de

i8CVS Domenico