> If you modeled this, did you include loads in the centers
> of the
> elements that go to other radios that model the effect of
> the
> feedlines terminated in the stubs and bandpass filters for
> the other
> radios?
Modeling a system like this is very complicated since the
input impedance of the radio on receive and the output
impedance of the PA stage on transmit when looking back into
the PA sets the load on the transmission line for the
non-excited yagi section.
Then, since that is almost certainly a large mismatch, you
have transmission line effects to add in.
You'd either have to know all the information exactly, which
no one does, or assume a worse case condition and play with
loads at the antenna until coupling is maximized.
A better solution would be a very high Q shunt system at the
feedpoint of some known distance from the feedpoint that
establishes a near zero impedance at the undesired
frequencies. That would make it easy to model interaction.
The bottom line is to be safe we need isolation within
several dB of the value a common feedline would require. It
certainly does simplify splitting and combining, but not
filtering to any significant extent. Expect big smoke
without the filtering.
73 Tom
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