What of the freqs are tx and which rx? If you're trying to Tx 442.750 and
448.025 and Rx 447.750 and 443.025, forget it, you can't duplex a 275 kHz
effective split, it's just not going to work. I won't get into the hazards
of in-band linking, but assuming your repeater antenna is an omni, it's
really pretty poor practice to be transmitting omni for a point to point
link, especially on a repeater input frequency, if this is the case...
If the splits are tx 442.750 and 443.025, with Rx'x 5 MHz above, the narrow
differential works in your favor and would allow for combining with a hybrid
ferrite combiner (about 3.5 dB loss per leg), use a pass/reject duplexer
with a relatively low-Q pass response that will pass both (I've done this
with PD696's duplexers at 150 kHz and 200 kHz spreads at two sites, could
probably have stretched a little wider even), spread the notches slightly to
get enough rejection at both freqs and/or add an extra cavity if necessary,
and power-divide the Rx port of the duplexer to both receivers.
You could do cavity-ferrite combining at 275 kHz, but the losses won't be
much less than using hybrid ferrite. If you went that route with something
like a Tx-Rx T-pass combiner you could put the Rx ports right on the
backbone rather than having a separate duplexer.
Maybe a better idea is to shoot the link on a different band (222, 903,
1296) and diplex on the 440 feedline to a little yagi on the same mount as
the repeater antenna?
--- Jeff
--------------------------------------------
Jeff DePolo WN3A - [EMAIL PROTECTED]
Broadcast and Communications Consultant
> -----Original Message-----
> From: Chris Peterson [mailto:[EMAIL PROTECTED]
> Sent: Thursday, November 04, 2004 7:25 PM
> To: [email protected]
> Subject: [Repeater-Builder] combining a UHF link radio and a
> UHF repeater on one antenna
>
>
>
> Hi all,
>
> My repeater is moving to a watter tower which will double
> it's coverage
> area.
>
> Here is the problem. The feed line path up the tower is full
> enough that we
> can probably fit only one run of feedline up the tower.
>
> The link radio is on 443.025/448.025 and the repeater is on
> 442.750/447.750.
>
> With this small split, is it remotely possible to combine the
> link radio and
> the repeater to use the same antenna?
>
> Another option may be to run a fairly small feedline for the
> link radio,
> I.E. LMR-400. This is about a 200 ft run of cable so I
> imagine the LMR400
> would be pretty lossy.
>
> Any thoughts?
>
> Thanks,
> Chris, KG0BP
>
>
>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
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