[TowerTalk] Triplexor/Switch/BPF SO2R

[ed_richardson at shaw.ca]

Regrettably I am resigned to never having stacked monobanders on this
suburban lot.  I have now started investigating the idea of using a
triplexor and associated bandpass filters as a way of getting an SO2R
antenna system operational utilizing the same 5 band yagi.  Currently I am
using a ground mounted vertical (during the winter only) as the second
antenna.

 

The common application recommendations are to use one of the 2x6 or 2x8
switches to direct the 20/15/10m signals from either transceiver through the
matching BPF and into one input of the triplexor.  I am seeing band to band
isolation figures of the filter/triplexor combos in the 85-100 dB
Unfortunately the 2xn switches appear to have radio A to radio B isolation
values in the 70 dB range.   

 

Would this multiport switch isolation not be the limiting factor? Two 1 kw
transmitters will still place -10 dBm signals at the input of the other
radio.

How critical is it that the unselected bands be terminated in 50 ohm?  I see
that many of the 2xn switches ground the unselected ports and this would
effectively put a short on the unused BPS filter input.

 

Would a second set of low power BPFs installed between the radio and power
amplifier be effective in removing another 30-40 dB of offending signals.
This comes at the expense of another dB or so of insertion loss.

 

Does anyone have any real-world practical experience using two - 1kw radios
triplexor/filter/switches.  

Lessons learned are much appreciated. 

 

Ed VE4VT