iGoogle. The Real SWR Page - Explained by WC7I - Will high SWR burn up my radio? High loss coax can really reduce your output power. A coax with a 3 dB loss will suck up half the power, allowing the antenna to radiate the other half. End of part 1. Part 2 Antenna SWR Have you ever measured the SWR of a simple antenna? It should NOT have been 1:1 Lots of people think that a good antenna should have a 1:1 SWR as measured by an antenna analyzer. We need to look at what SWR means, and how an "antenna system" is different from a simple antenna. Unfortunately, we need some 6th grade mathematics for this explanation. One way to find SWR is to make a fraction of the coax and load impedance. SWR is really a simple fraction that puts the larger impedance in the top of the fraction, and the smaller impedance in the bottom of the fraction.
It is done this way so the answer is always equal to, or greater than, 1. Let's try this to see what I mean. SWR =72/50 = 1.44 which means the SWR is 1.44:1 Lets try this again using a 36 ohm vertical antenna with at least three un-grounded radials. K8ZT's Ham Radio Resources- QRP, DX, Logging, Contesting & Ham Radio. Callsign Database. KØBG.COM. American Radio Relay League | ARRL - The national association for AMATEUR RADIO.