Daniel
It is true that The band pass/band reject do offer some protection it
is not as great as many believe. See
http://www.anglelinear.com/repeaters/repeaters.html
for a description of the limited filtering of most Cavity type
Duplexers. We have duplexers from TX/RX and still needed additional
filtering on 146 and 442. Our 1.2 and one of our 440 duplexers come
from Angle Linear as do out PHMET Preamps.
We had thought about a triplexer for the 2 1.2 modules but the wait
was too long and we elected to go with 2 antennas (one for each
module) and frequency separation 1285HHz - 12MHz for DV with a
duplexer and 1255MHz for DD as of now we haven't had any problems -
the 2 antennas are about 20' apart, The Duplexer on the DV module is
a 7 section unit with PHME preamp from Angle Linear.
Bob Cumming
W2BZY
(for K1XC & W4PLB)
At 03:50 PM 4/20/2010, you wrote:
Bob,
All good advice, however I would like to add that there
are a number of duplexers out there that do both pass
and reject such as TX/RX and Wacom (both the same
company now I believe) and there are some other ones
as well. I like the TX/RX vari-notch design where all
cans in the duplexer have Pass/Reject capabilities.
Another way to deal with this is to use seperate antennas
at different heights on the tower. Vertical seperation gives
an amazing amount of isolation. Right now we are running
VHF and UHF on a combiner/multicoupler with 4 antennas
involved, and of course we are sharing that with several
other systems as well. For 1296 there is a single antenna
and soon we will see the arrival of our Triplexer from
TX/RX that is a cross between a duplexer and combiner
that allows both the Data & Voice modules for 1296
to operate on one antenna.
Dan Thompson
<mailto:dan%40waycom.com>[email protected]
Bob Cumming
W2BZY
