HFU HF Underground

Technical Topics => Equipment => Topic started by: K2BUG on January 16, 2016, 2257 UTC

Title: High SWR in a cushcraft A3S yagi
Post by: K2BUG on January 16, 2016, 2257 UTC

Hi,

Measured SWR in my coax with an antenna analyzer into a Crushcraft A3S yagi which is tuned to 10, 15, 20 m.  I also have the 40m add on kit.  SWR is now 10-12 across bands.

Is this feed line contamination?  Other causes?

Thanks

Title: Re: High SWR in a cushcraft A3S yagi
Post by: redhat on January 17, 2016, 0823 UTC

Water in a connector, carbon trail somewhere in the coax, probably something like that.  Try connecting the analyzer to the antenna with a known good jumper and all will be known.  Could be water in the antenna's matching system too.

+-RH

Title: Re: High SWR in a cushcraft A3S yagi
Post by: Stretchyman on January 17, 2016, 1019 UTC

Could be ANYTHING!

I'd terminated the coax at the anternna end to rule out the feeder first.

it's fed directly so no fancy matching.

Str.

Title: Re: High SWR in a cushcraft A3S yagi
Post by: K2BUG on January 17, 2016, 1240 UTC

Ok, thanks

Since it is winter in upstate NY and the antenna is mounted on top of my 3 story house with a steep roof, this project will have to wait until late spring or early summer.

Title: Re: High SWR in a cushcraft A3S yagi
Post by: syfr on January 24, 2016, 0005 UTC

I have one of those antennas. If it's high SWR on all bands, I'm guessing that it's a coax problem.

Swap the coax and let us know what the result is.  The outboard parts of the radiating element aren't even seen , say if you're operating on 10m, so if it's that high on ALL bands, it's probably the most simple reason...

Bad coax or coaxial connectors.

Disconnect the coax at the feedpoint and connect it to a dummy load and see what you read.