James barrett wrote:
Hi, I don't understand how you can add elements to an existing antenna
and have it still work on the band it was originally made for. Do you
still need a tuner? Or do you remove the 20m elements to transmit on
10m?

The RF source energy will follow the path of least
impedance. If we have dipole elements for 40m, 30m,
and 20m on the same antenna, when we are on 30m, for
instance, the 30m dipole has a low impedance while
the 40m and 20m dipoles both have high impedances
to the 10.125 MHz source signal. This configuration
can function without a tuner.
--
73, Cecil http://www.w5dxp.com