Late in 2018 I decided to experiment with trying to load my 160m antenna on 630m. I built the 200 to 350 uh variometer and a tapped impedance transformer on the left. This configuration when properly tuned provides a 2:1 bandwidth of around 7-8 KHz. This is not a permanent configuration as I must set everything up ahead of time and then cannot use the antenna on 160m. Feel free to drop me an email with questions.
On topband the transmit antenna is an inverted-L with (32) 1/4 wavelength ground radials. This is a seasonal antenna as the radials are rolled out on the back lawn in late October after the leaves get raked up each year and then rolled back in when the snow melts in April.
At left is the 160m inverted-L feedbox with the front cover removed showing the 1000 pf vacuum variable capacitor installed in series. The overall length of the antenna is slightly longer then a 1/4 wavelength and the capacitor can be adjusted to resonate the antenna anywhere in the band. This configuration yields a 2:1 SWR bandwidth of 67 KHz (see SWR plot).
In 2009 I installed a K9AY loop to improve low band reception. Like anything else on topband this was a compromise due to real estate constraints and the close proxmity to other low band antennas.