My SWR Is Low. Why Am I Still Losing Signal?

Station Physics · Answered

My SWR Is Low. Why Am I Still Losing Signal?

Short answer: SWR measures the mismatch, not the loss. Coax turns part of your power into heat on every foot of the run, and a low SWR reading says nothing about how much. Loss has to be calculated from the cable type, its length, and the frequency.

Why the meter cannot see it

An SWR meter in the shack compares the power going out with the power coming back. But power lost as heat in the cable never comes back to be counted — so a lossy cable can actually make the SWR look better than the antenna really is. Walt Maxwell, W2DU, spent a career teaching hams exactly this in Reflections.

What makes loss grow

Three things: length (every foot adds loss), frequency (loss rises as you go up the bands), and cable size (thin cable loses more than thick). Mismatch on the line adds more on top. The same loss works against you twice: on the watts you send, and on every weak signal coming back.

What operators see when they fix it

Gary Kalata, KC4ES, changed nothing on his antenna — only his cable, from RG8X to LMR-400. His words: “What an unbelievable improvement that made, 80 through 6 meters. I went from a good antenna to a great antenna.” Run your own numbers in the Feedline Loss Calculator.

Jon Kimball, KL2A · Greyline Performance · 435-200-4902