Bob,
The suggested trap idea might well be the best solution for the antenna to
work on both 80 and 160, given that the single antenna is a constant in
the installation equation.
Tuning the trap to about 3.4 MHz or thereabouts will maximize performance
on both bands. Yes, a trap will give a bit of loss, but if you m,aximize
the component Q, and tune the trap below the higher band by about trhe
amount indicated, losses compared to a full size dipole for each band will
by about 0.15 dB, an acceptable loss in most cases where installation
mechanicals set restrictions on what can be done. Of course, the
antenna's overall length will be shorter, with the trimming on 160 due to
the remnant reactance in the trap.
I do not have figures on lengths, but you should be able to find the
lengths for the inner and outer sections in a straightforward manner. Set
the traps and adjust the 80 meter section for resonance with the 160 meter
wires in place. Then trim the 160 ends for resonance. You can readjust
the two sections one more time and find the desired final positions.
Hope these notes are useful.
-73-
LB, W4RNL
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