View Full Version : SIRIO SWR Pre Adjustment.

Big Ed
12-22-2021, 09:49 PM
Hello All, So I decided to build a new antenna mast, I'll be around 42' in the air including the antenna which is a SIRIO GPS 1/2, I'D Obviously like to pre tune the SWR while its on the ground to get as close as I can to a 1.1 or 1.5, I'm not to sure about the tuning table instructions though as I've never done this, I want to adjust the L Gap to the 27.185 freq range which reads 660MM, I believe 660MM is around 26 inches? that seems like it will be way to high, had a buddy tell me 9 inches for the L Gap. I'm not sure what to do now. Thx for any help.

12-24-2021, 01:00 AM
660MM=26-63/64 I looked up a metric converter online.
Suggestion, before taking antennas all the way up the mountain at my old job Id mount it on a fence post with plenty of free space around it and tune it as close to 1.0 as possible. In that way I was already pretty close and had minimal adjustments to do on the tower.

02-25-2022, 06:07 PM
Most of those antennas have fixed lengths and if assembled correctly will have the best SWR you can attain. Be sure not to leave out any gamma, beta, or hair-pin matches (even if they appear to physically short-circuit the antenna between the driven element and the radials) An SWR of 1:1 on channel 19 is usually attainable with a 1.5:1 on channel 1 and 40. SWR of 1.5 translates to 96% of your power exiting to the sky. SWR of 2.0 translates to 89%.