Visual Mismatch


As it turns out, the 60-ish feet of 50ohm RG-8 coax feedline I “rescued” from the disused tower at my last office is actually 75ohm T-1253A. I should’ve looked at the silkscreen more closely. I’m a blind fool.

That might explain some of my inability to match my antennas on some bands. The SWR will never be better than 1.5:1, even if the line length is exactly a half wavelength. The velocity factor is different than I expected, and because of the worse SWR, my line losses are higher, even on short runs.

Yeah. This is the same “RG-8” that I have feeding the 2m/70cm antenna I just posted about. The losses on those two bands swings from 1.6db to 4.8db. A major mistake!

I mean, it’ll still work of I know what to expect. 75ohm cable is easier to source and cheaper to buy, so lots of hams use it with precaution. Until then, I should look at getting a reel of actual RG-8.

Radio is hard.

Published by Shawn

He's just this guy, you know?