SWR fluctuates

[Boll Weevil]

I have been running a 4.5 Francis with SWR readings of 1.2, 1.2, and 1.3 0n ch's 1, 20, and 40 respectively. Since I don't have the sense to leave well enough alone, I decided to try my Wilson 2000 on the same mount. When keying on ch 20, the SWR will reach around 2.1 and immediately drop to approx. 1.6. What would cause this?

Thanks.

 

[hookedon6]

funky meter?
R.F. affecting the meter?
intermittent coax connection?

 

[midnight special]

harmonics?

 

[Boll Weevil]

I was comparing the 2 antennas using the same radio, same vehicle and parked in the same spot. I was using the built in meter on my Stryker 655 which I figured was good enough, at least for comparison purposes.