I wasn't clear about that...the motivation for rebuilding it is that
most of the equipment at the voting sites is gone. Just one rcv
cavity, and the antenna system at one site remain. I don't even know
what was installed there. Also, only one of these sites is still
available. I think we'll run 3 voting sites in the end, so we're
looking for two more. That's what I've got to work with.
At the main site, the current setup is a Mitrek receiver, a heavily
modified Kenwood TK-930 transmitter that can put out around 13W
continuous, driving an amp (can't remember what) with a single
MRF-174. It puts out about 85W into the duplexer. The TK-930 is brain
dead, so temporarily, I have put in a CDM-750 running 25W without the amp.
There's a box with 3 MSTR-II UHF receivers that used to listen to
voting sites connected to an LDG RVS-8. Each receiver is connected to
it's own beam antenna. These look OK.
That's what I've got to work with.
--- In Repeater-Builder@yahoogroups.com, Nate Duehr [EMAIL PROTECTED] wrote:
tedsims wrote:
I'm hoping that I can identify equipment that seems more familiar to
me on the inside (PLL synthesis, SCF audio processing, LDMOS, surface
mount). I know the MASTR II, Mitrek, etc. are very fine radios, but
the inside of one of these looks completely alien to me. Any
suggestions?
What's broken/breaking in the system today? (In other words, what's
the
motivation to re-build it?)
What's the budget like? A modern voted system like that with all
new(er) rigs could get real expensive, real fast.
Here's how it probably goes...
The older stuff (like the Micor and MASTR II) are at least considered
modern up through the 1980's. (They were still available new from
the
manufacturer close to 20 years after they first hit the market, which
says a whole lot for their design-quality and ability to work
seemingly
forever. A lot of clubs/groups are still running them without any
more
than a quick trip to check sensitivity and PA output power, etc... once
a year. If even that.
The used market is flooded with this year right now, but won't be
forever.
One of the positives of some of this older gear is that the complete
board assemblies on SOME of these models, are directly from the mobile
rigs. The mobiles are so old now, they're getting to where they're
very
inexpensive in BULK if you find an auction, or similar... and you are
willing to swap boards and see what's working and what's not. You can
build a mighty spares pile of known working receivers, exciters,
etc... for the older repeaters from mobile boards. (I'm a MASTR II
fan, the Motos I hear this is harder... Moto didn't make their stuff
as interchangeable. I don't know. Your mileage may vary.)
In the mid-80's gear like you're describing with more modern
components arrived. But it was done on the cheap as far as actual
RF-design goes, with many of the rigs made overseas and of questionable
build quality. The front-ends are quite a bit broader, even though it
added sensitivity... etc. For links and receivers at high sites, this
is often backward of what you're trying to accomplish... and you end up
putting a lot of out-board filtering on the pile of receivers at the
voter site... to keep the out of band stuff nearby from bothering them.
Systems like the MSR-2000, later the MSF-5000 from Motorola and the
MASTR III from GE/MA-Com came out as replacements for the gear
sold in
the early 80's.
The MASTR III is still current product at MA/Com, the MSF-5000 as
far as
I know is. They're still built like real repeaters... and anytime
you
have the space in the rack and the money to pay for them, they're well
worth it. But they (especially NEW) are NOT cheap.
For a ham radio voted-system, the sheer number of TX/RX pairs you need
means you probably can't afford a rack full of nice solid commercial
gear like that. Size, power consumption, amount of space needed in the
racks... etc... would be too great. So the pile of mobiles on a
shelf
thing is often done instead.
Options would be things like others have already mentioned...
commercial
mobiles from the mid-80's like the GM-300/Radius series from Moto,
etc... that have the appropriate connectors on the back (16-pin) to
give
you the right connections needed to deal with voting systems... etc.
For the TX part... running some of those rigs in their 10W varieties
works, but it's still just a mobile rig. Try to keep them cool.
(Which probably means adding fans to your PA heatsinks.)
Basically, if you go this route, you're trading quality for quantity,it
works... but make sure you're planning to have spares sitting around,
pre-programmed, ready to go when you blow up a link radio in that
environment. Since mobiles are generally cheap.
Other interesting possibilities include using Kenwood TKR-series
repeaters as the links... (expensive, but nice...), etc
