As it's unlikely you've changed the laws of nature it's probably your coax. Put a 50 ohm dummy load on one end and connect your analyzer (or even your rig) to the other and do a sweep of frequencies. I remember once having a cable that must have had water ingress that caused all manner of swr problems that seemed to change on a daily basis.
73 Sholto --- In [email protected], Andy obrien <k3uka...@...> wrote: > > Hmm. My homemade 20M Ground Plane antenna that was nicely resonant on > 20M now has a 3:1 SWR on 20M but is 1:1 on 30M! Perhaps I should > patent the design, how to make a resonant 30m vertical out of 17.5 > feet of aluminium tubing! The other odd thing is that the SWR is only > around 3:1 on 10M, 12M, and 15M. I would expect it to be much higher > without tuner. It is not until I get to 40M that I get a very high > SWR. I'll be going outside to check , when the weather clears. It > will be interesting to find out what has happened > > Andy K3UK >
