I just installed one of these and did a lot of experimentation with the
tuning rings. This is a truly great low cost antenna for the higher
bands. I use it on 10, 12, and 15 meters. My worst swr is 1.45 to 1 on
15 meters.

The bad news is that the owners manuals tells you to cut a foot off the
top whip to tune this for 28.4 mhz. This would be a very bad move. I
tried this by installing a whip that was already a foot shorter. It
could be tuned for 28.4 but not for the other bands.

This antenna can be tuned for a 1.0 to 1 match on 28.4 with just the
rings. I settled on a compromise that gave me a 1.2 to 1 match on 28.4,
a 1.3 to 1 match on 24.950 and 1.45 to 1 match on 21.35 mhz.

Do not install the ground plane kit. This narrows the bandwidth to be
unusable for hams.

The price for this antenna rated at 2000 watts is about 110 bucks
shipped. Hard to beat this performer. I only use 600 watts on these high
bands. I use 1500 on the lower bands where you really need it.

And no I have no relationship with solarcon other than being a happy
buyer. If anyone is interested, my rings wound up beings set at 4 turns
down from the top most position possible.

Michael