Post by denniskb7st on Oct 23, 2010 17:34:26 GMT -5
I was trying to find any posts on the return loss parameter on this forum and searched for the last year, but nothing came up. I tried several other search phrases of items I knew were in forum posts, like some of my posts. Again nothing displayed. I'm hesitant to post a questions when they have been covered before but confused why I'm not seeing anything. If I search on my callsign KB7ST, it does return my posts. Any ideas on what I'm doing wrong?
As for return loss, I'm trying to figure out whether AIM will show me the cable loss for my 182 feet of RG-59 to my 40M sloper. At F resonant, it shows Return Loss -3.45 dB at 14.025 mHz. TLW program shows cable loss as 2.23 dB for that 182 feet. I checked some web sites that say "The return loss is simply the amount of power that is "lost" to the load and does not return as a reflection" So, I guess I'm mixing two concepts. When I searched the manual for return loss, it didn't explain the context or how it is arrived at.
The cable loss shown on the right side of the screen is valid when the cable is open (or shorted) at the far end. This is a measure of the power lost in the cable itself. When the cable is open or shorted, no power is lost in the "Load" since there is no load.
The return loss is twice the cable loss since the power applied at the transmitting end travels twice through the cable (down and back) and by the time it returns to the detector, whatever cable loss there is has been subtracted twice from the wave.