I see that English isn`t your mother tongue then !!!.......or are you just
kidding??.... ;-)

Lee......G6ZSG.....

"an_old_friend" wrote in message
oups.com...

Dave Platt wrote:
In article .com,
an old friend wrote:

haing gotten many of the peices of a 222 band repater and wanting to
put it on the air how much sepertion is required to avoid a paying the
price of a duplexer at 22 band
cut for brevity
My old copy of ARRL's "FM and Repeaters" book (copyright 1972)
suggests that approximately 58 dB of attenuation is required for a 600
kHz transmit/receive offset. They don't give a suggested figure for
the wider 1.6 MHz offset used on the 222 band.

According to the graphs in this book, achieving 58 dB of attenuation,
on the 222 band, requires approximately 20 feet of vertical separation
between antennas, or approximately 100 feet of horizontal separation,
assuming unity-gain antennas (e.g. halfwave dipoles). You'd need
greater horizontal separation when using antennas with gain over a
halfwave. You might be able to get by with less vertical separation
if using gain antennas, depending on the actual pattern, feedline
radiation, local reflections, and so forth.
ty for that given the proposed is a pair of disused grain silos 80 feet
a part I was thinking horizontal sepertion (frankly had not considered
vertical at all or i would have made that

You might want to Google around for articles which show a method for
homebrewing a duplexer, using a length of surplus large-diameter
hardline coaxial cable as the resonator. These have apparently been
used for several years on the 6-meter band, and I recently saw a
Heliax notch/pass resonator which was made for a local 2-meter
repeater (it adds one additional section of receive
filtering/isolation to a repeater which uses a single antenna and a
commercially-built two-transmit-can, two-receive-can duplexer). The Q
of such Heliax-based resonators is lower than that of conventional
cans, and the insertion losses are higher.

If you don't want to install a full-fledged duplexer and use a single
antenna, you might try something like a pair of 222 antennas with 20
foot or more of vertical separation, plus one band-reject (or
band-pass band-reject) Heliax resonator on each one.

http://www.dallas.net/~jvpoll/dup6m/dup6m.html would be one place to
start looking.
I had read something of that but have never been any good at cuting
stuff right (i end up with lots of scrap

i have just hearing folks with with radio that have some 22 band (a
kenwood tribander has been popular round here) and no reapters localy
that use it I am planing on trying to put together a decent repater
that work at least out then goping after I ge it u and let be know at
that point it exists maybe some folks that could help with hombrewing a
duplexer will step up to improve the system

ty for the info

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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