John, for your application I would suggest buying a GE Mastr II mobile UHF
radio and modifying it for repeater use. It is very simple to configure, and
all the info you will need is on the repeater-builder site. I have several of
these units in service and have been very pleased with the results. If you do
not care to do the modification yourself, purchase one of these units from the
repeater-builder folks.
In my experience they far out-perform the Hamtronics type units so far as
reliability and desense rejection is concerned.
I think you are on the right track for your system. As you might remember, I
suggested this solution in the first place. Use a standard VHF duplexer to
couple the two radios to the VHF input of a Comet or Diamond band splitter and
couple the UHF duplexer for your repeater to the other port of the band
splitter. A dual band antenna will complete the RF configuration with a
minimum of difficulty on the RF side.
To avoid complications on the two packet ports, I would configure the system
to not allow transmission on both radios at the same time. Packet TNCs have an
input to prevent transmission when a signal is being received, and you should
be able to arrange logic to OR the receive signal DCD with the PTT on the other
radio and supply this to the TNC as the DCD signal. Do this for each TNC,
using the other TNC PTT signal. This will avoid the possible intermod product
you will generate with the two transmitters keyed at the same time. If your
two packet frequencies are exactly 600 kHz apart, the other 2 meter repeater
owners in the area will apreciate it also.
73 - Jim w5ZIT
John Barrett <[EMAIL PROTECTED]> wrote:
The major problem I was having is resolved. Ive finally got a
UHF backyard pair for my portable repeater J No more hassling with trying to
pack 4 radios into 1mhz of VHF bandwidth J
Since there isnt a way to look at receiver specs and figure how much
isolation is really needed, here I am asking what is my best bet for radios
to build a UHF repeater? Im currently looking at a Hamtronics receiver/exciter
pair with separate PA, but Im pretty much open to anything I can get at a
reasonable price (300-400 for both RX and TX, PA extra if needed). The repeater
controller I will be using has PL built in, so the radios dont need it. I
would prefer 50 watts or better output, 100w max.
Size is important. Ive only got about 16 of depth to mount this in, though
there is a way I can get bigger than that if absolutely necessary. If the
equipment recommended has any front panel controls, it needs to be 16 or
less front to back. If no controls, then I have a lot more freedom in mounting.
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