Hi Kevin,
Anything is possible with enough resources and
time, it's just a question of how practical...
You could make up a close spaced combiner/duplexer
but it's not going to be easy with "regular parts".
A conventional duplexer would not work very well
at <1MHz spaced. Many are rated at 5MHz while a
few are rated down to 3MHz typical.
You're talking a very High-Q path of large bottles
in band-pass and notch-out layout using 12 to 15"
high Q bottles. I made one for 250KHz spacing and
it wasn't easy. The assembly will be pretty lossy
and/or have a relatively high insertion loss.
Better to run dual vertical spaced antennas with
series bandpass bottles in each leg, keep the feed
line spaced more than 1/4 wave from each other
(yes feed line spacing... as even hard line leaks).
Put the receiver antenna on top. Get as much
vertical spacing as you can.
cheers,
skipp
> "Kevin" <[EMAIL PROTECTED]> wrote:
> Hi All,
>
> I am buidling a 470Mhz PRS here in NZ.
> However on checking the frequencies for RX/TX, I found it was very
> close, less then 1Mhz. For the channel they will be using, it is
> 476.425RX/477.175TX.
> I am sure the radio will be okay, however I am a little concerned
on
> using 1 antenna, and running a duplexer.
> Question: can a 70cm duplexer be made to work at <1Mhz, and if so
what
> type would he need?
>
> Any information would be helpful.
>
> Regards
>
> Kevin, ZL1KFM.
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