Re: [TowerTalk] Force 12

[VR2BrettGraham <vr2bg@harts.org.hk>]

W6RMK asked:

> > In order to get a reasonable match, perhaps, but wouldn't being able to
> > use one C-3 on >1 band simultaneously be a good reason to go with
> > separate feeders?  ;^)
>
> And there's a demanding test for the IP3 of all of your receivers' front 
> ends...
>
> I assume you plan on running a kilowatt on each band?

Wish our power limit allowed a kW.  ;^)

With a little extra bandpass filtering, lots of folks who can run 1.5 kW are
listening on one band whilst CQing on another with a dozen or two of cm
separation between driven elements.

I find the limiting factor is more wide band noise from the transmitter rather
than the receiver wilting, but dealing with the former makes the latter pretty
much a non-issue.  Portions of my current antennas are single-digit cm away
from each other & when I get around to adding stubs, I should be able to
listen within a few kc of even the harmonic of one rig that falls within the
other band I'm listening on with the other.

All my antennas are in roughly a 8 m^2 space.  The tower supporting the
higher band antennas is even shunt fed for the low bands & is being lit up
whilst the other rig is listening on the higher bands.  One of these days,
I might hang a spectrum analyzer on the feeders to see how much isolation
I start out with before the filters, but it's probably so little I'd rather 
not know.
I envy even second or third tier stations in other places that have the
luxury of a little space.

73, HL1/VR2BrettGraham

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