--- In [email protected], "Robbie" <[EMAIL PROTECTED]>
wrote:
>
>
> I am in the process of learning how to build a VHF repeater from
two
> stacked Vertex VX-4100 VHF Mobiles. I have never done this before,
> and am a little frightened. I recieved an email from vertex on how
to
> hook up the cabe between the two radios D-Sub connectors on the
back.
> It seems pretty much plug and play except for having to place a
300k
> resistor in line( I think that is what frightens me ). I chose
Vertex
> because I distibute for them, so therefore, I have the programming
> software and the cables. I know I need a duplex, which I am still
> looking for( The object is to build a cheap repeater :) I have the
> antenna already, it is a Decibel Products VHF Dipole antenna with
4
> bays. I got it free, and I think those things go for big $$$. Has
> anyone ever built one of these before, or a similar setup ? If so,
> what are some of the +'s and -'s of building this vs. buying a
> conventional VHF reapeater ? Thanks in advance
Well, I will take a stab at this, because no one else has yet. That
is probably because this subject gets covered here quite often.
I cannot speak for the Vertex, because I've never used any of their
equipment. I have built a few repeaters with Motorola mobiles using
a RICK. (GM300's - MaxTrac's)
I suppose an advantage would be slightly less cost than a
conventional repeater, but that is relative. You might be able to
pick up an old Micor repeater for less money, but if you are not a
seasoned repeater builder, setup could be a nightmare for you.
The big disadvantage to repeaters built with mobiles is "duty
cycle". This is where a lot of first timers get the wrong idea. If
you are building this for the amateur service - forget it! I'm sure
a few will jump in here and disagree like heck. It can be done, but
it is not plug and play. Those that have built amateur repeaters
this way have done mods on them to make them able to survive. If it
is used for emergency or short term backup, you are probably OK.
If it is being used for commercial or GMRS (if the radios are type
accepted for it), you will probably be OK.
Duty cycle (with the power turned down and fans used)will be 25% at
best. Transmit 25% of the time, receive 75% of the time. Even with
the power turned down they still will get very hot under heavy use
and will eventually die an ugly death. I know! I've done it!
Good luck!
Gary KB7TRP
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