Ken- consider that these are a high "Q" device (narrow bandwidth)
and, that they are a tuned loop (the ends of the two rods form a
CAPACITOR-- and the plates of a capacitor increase capacitance, the
closer they get! The higher the capacitance, the lower the frequency.
The antenna , itself , is an inductor, and that INDUCTANCE doesnt
change.
"Tis that simple-- Jim NN7K

Ken Bessler wrote:
I got a AEA halo for 6m and put it up. Worked good but the
low SWR point was 51.000 with a 1mhz 2:1 bandwidth.

I wanted to adjust it so I got a 1:1 SWR at 50.500 so I took
it down and loosened the loop overlap screws. I then stretched
the loop out 2", figuring longer = lower freq.

The low SWR point CLIMBED 800 khz!?!?!? WTF?

I pulled it back down and made the antenna *shorter* than I started
and bingo! It now shows 1:1 SWR at 50.500 mhz yet still shows
acceptable SWR on the local 6m repeater's input (51.130). 52.525
is out - SWR too high. :-(

Will someone please explain why this antenna seems to defy
conventional tuning standards?

Ken KG0WX