View Single Post
  #5 (permalink)  
Old 05-19-2017, 6:53 AM
prcguy's Avatar
prcguy prcguy is online now
Join Date: Jun 2006
Posts: 6,497

Two things potentially going on here. Whatever the match is on the antenna, it will be apparently reduced when you have loss between the SWR meter including coax loss. If you have a 2:1 match at the antenna it could look like 1.5:1 or less depending on loss. If you upgrade the coax to something with less loss it will show a match closer to reality, meaning your LMR400 could be showing you a more realistic match on your antenna.

Another thing is the IMAX200 and similar antennas are poorly decoupled from the feed line and the feed line will radiate some. The particular length of coax you use along with the mast length can change the match slightly. It could be you found a lucky bad coax length that affects the SWR in a bad way.

You should measure the match right at the antenna with the meter on the antenna for a sanity check. If its 2:1 then the LMR400 is showing you what's actually there. If its a great match at the antenna then add some odd length jumpers and see if the match stays constant or wanders all over the place with different lengths of coax.
Reply With Quote