My recently installed shunt feed for 80 meters worked so well in the CQ WW
contest (60 countries, 22 zones from northeast Louisiana) that I now want
to build one for 160 meters on the same tower to utilize the same radial
field.
My desire is to be able to have an 80m transceiver connected to the 80m
feed, AND at the same time have a 160m transceiver connected to the 160m
feed. My installation uses individual feed lines per band all the way back
to the shack.
The challenge as I see it is the direct connection of two feed lines to the
same radiating element (the tower) at the same time. It is my understanding
that AM broadcast stations sometimes do a similar thing to share a tower for
multiple frequencies.
Using the power ladder in W2VJN's book, it is clear that my proposed
installation would require many dB of isolation between the two bands. From
what I understand in George's book, stub filters will get me part of the
isolation needed.
Has anyone been successful in accomplishing this type setup?
What technique(s) did you use to get the needed isolation?
Certainly, an active feed line switching and lockout system would work, but
relying on that alone would be disastrous if a relay or other component
failed at an inopportune time.
I would much rather have passive components or devices doing the isolation.
--Scott, W5WZ
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