> 1. Mounting the dipoles and harness from a UHF DB420 on the same mast
> as a VHF DB224, or vice versa. (UHF and VHF antennas on the same
> mast)
There will be a lot of interaction between the two. I wouldn't do this.
You'd also likely need extra filtering on the ground between the VHF and UHF
repeaters since the coupling between antennas will be very high.
> 2. Mounting the dipoles and harness from a DB420 on the same mast of
> an existing DB420.(2-DB420 UHF antennas on the same mast)
Really bad idea. At that point, you may as well just use one antenna and a
combiner/multicoupler at the bottom - you'd likely need almost the same
amount of filtering with the two antennas "separated" on the same mast
because there will be so much coupling.
> 3. Taking an existing DB420 antenna and feeding the upper and lower
> halves with separate feedlines to make 2-6 Db antennas on the same
> mast. The lower harness section would be replaced with with the upper
> harness section from a junk antenna.
Better idea. This used to be order-able as a DB420D, which was really two
DB408's on the same mast, one stacked above the other, with the feeders for
both antennas terminating at the bottom. The isolation between antennas was
something like 30 dB, so again, you'll still need adequate filtering
downstairs.
> If any of the above ideas are practical this would allow me to recoup
> some additonal mounting positions or at the least reduce the clutter
> of antennas I have now.
Can you mount two antennas on the same mount, one rightside-up, and the
other inverted? If you do this, be careful if you invert-mount a DB420.
The mechanical connection in the center relies somewhat on gravity to keep
the two halves together; if you invert-mount, gravity is working against
you.
--- Jeff WN3A
