I build my own diplexers. This way I can insure that the components are
suitable for the power level used.
The 440 side is built in typical antenna tuner fashion with a series variable
cap, a shunt inductor and a series variable cap. Adjust the caps to provide a
1:1 SWR at the operating frequency.
The 2 meter side is built using a series inductor, a shunt variable capacitor,
and a series inductor. Adjust the capacitor for a 1:1 SWR at the operating
frequency. If a 1:1 cannot be obtained, spread or compress one or both of the
coils to get 1:1.
The theory behind this set-up is that the small capacitor value required to
tune the input on the 440 side has negligible effect on the 2 meter frequency,
and the input inductor for the 2 meter side looks like an RF choke to the 440
side.
Make sure the inductors do not couple to each other and a very successful
coupler with added SWR correction, if needed, is possible. A hairpin loop is
all that is required on 440 with a couple of 10 pF variable caps and a 20 pF
variable cap for the 2 meter tuning with a couple of air wound inductors of 2
or 3 turns will work.
I have built these couplers for powers up to 100 watts and the power on one
band does NOT add to the power on the other band. Just choose the components
and wire sizes for the power level required.
73 - Jim W5ZIT
--- On Tue, 9/23/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
From: [EMAIL PROTECTED] <[EMAIL PROTECTED]>
Subject: Re: [Repeater-Builder] VHF and UHF repeaters on one antenna
To: Repeater-Builder@yahoogroups.com
Date: Tuesday, September 23, 2008, 9:50 AM
At 9/22/2008 19:10, you wrote:
>I've been running an MSR-2000 on a
>Tram 1481 antenna on 146.72 with
>a Sinclair Q2330E duplexer and it
>works fine.
>
>I just got a retired Motorola UHF
>repeater (C64RCB-3105AT) with a
>Sinclair Q-306D duplexer and was
>wondering if I could use both
>repeaters on the same antenna.
>
>Would I be able to get away with a
>ham-type VHF/UHF "duplexer" like
>a Comet CF-4160K?
Yes. Just make sure it's the model without pigtails, & be careful if
either of the repeaters runs more than 50 watts. The combined TX power
rating will probably be lower due to capacitor voltage ratings being the
limiting factor as opposed to heating.
Bob NO6B
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