Just an idea....
Diplexers are very popular for running VHF and UHF transceivers into the same (simple) antenna. This works since 435 is three times 145. A 1/4-wave radiator for the 2m-band is a 3/4-wave radiator for the 70cm-band.
Could this trick work on shortwave too? The 10m band is about a third of the 30m band ... well... sort of. I figure, I suitable diplexer would separate frequencies below and above about 20MHz, maybe 19MHz for good measures.
The hope is that a vertical of about 7m length would form a 1/4-wave radiator for the 30m-band and a 3/4-wave radiator for the 10m-band.
The numbers tell the following story:
wavelength for 30m: 300/10.14=29.6
wavelength for 10m: 300/28.32=10.6
30m radiator length (assuming a velocity factor of 0.95): 29.6*0.95/4=7.03
10m radiator length (assuming a velocity factor of 0.90): 10.6*0.90*0.75=7.15
A compromise could therefore be a radiator length of 7.1m to suit the 30m grabber and the 10m MEPT at the same time.
Next step, think of a 19MHz diplexer design.
