DaveM said:
The frequency difference might be insignificant if your antenna tuner can
accommodate the differences. The 10-meter band is lower in frequency than the
11-meter band, therefore all elements would have to be lengthened by a small
amount to get it exactly right.
Sorry, it's not. The eleven meter band, aka CB, is in the 27mHz range.
The 10m Ham band is 28.0 to 29.7 mHz, but most people don't use the
whole band. 28.0-28.3 is mostly CW (Morse code) because the U.S. prohibits
usage of voice signals there.
SSB and AM voice signals are legal in the rest of the band, but most often
they are found in the 28.5-29.0 range. FM voice is limited in the U.S.
to 29.0 and up, and FM repeaters use 29.5 to 29.6 for TRANSMISSION.
While it would be best to shorten all of the elements, and move them closer
together, it is really only necessary to shorten the driven element
(where the radio connects) and the director (the one in front of it).
You can do it simply by measuring them and cuting off the ends to make
them 27/28ths of the size they were.
Modeling the antenna with computer software would save you a lot of
time and trouble, or carefully modifying it by cutting and trying it
with an SWR meter or an antenna analyzer.
Keep in mind that you need a valid ham license in most countries
to transmit on 10 meters. If you do not have a license and are planing
to get one in the future, don't bother modifying it. The difference
in reception is not really worth it.
Geoff.