[FedCom] Re: P25 Digital For or Against?

[Dave J]

You're both right..........

The digi part  shortens the range a bit  -  and the higher frequencies
shorten the range a LOT.  The higher the freq the more sites/towers one
needs for the same coverage.

In example,  Prior to SD going to it's "new" trucked digi system our state
radio system used low band  (30-50 MHz) for it's comms.  When they went to
the VHF trunked system (150-155) they needed almost 4 or more times as many
towers for the same coverage.

Those agencies getting sold on 800 MHz systems (or even higher in freq) are
going to need even ~far~ more.    And fact of life - the more sites required
to maintain adequate comms,  the more points of possible failure.

Go up even higher (1800-1900 MHz) and the number of sites required for the
same coverage increases ~far, far~ more.

Dave J
sd0044 at gwtc.net
====================================
----- Original Message ----- 



>
> >Excellent explanation Dave! You gave everyone a clear and easy to
> >understand difference in the "comms vs distance" argument regarding the 2
> >modulation schemes!
> >
> >Keeping Dave's explanation in mind, and going a step further, that's the
> >reason the cost of a "digital" system is so much higher than the cost of
> >a comparable "analog" system, there is more infrastructure (read:
> >repeaters and/or receivers) required to maintain good comms over the same
> >given area. If you need an example, look around at how many cell towers
> >there are in your neighborhood, I think you will agree, there are many
> >more now, than when analog 800 MHz cellular was the only game in town!
> >
> >Ty Logan
> >_______________________________________________


From: "John Wilson" <w4uvv at adelphia.net
>
>    You're mixing 800 mhz. cell operation with 1800-1900 mhz. PCS cell
> operation.  PCS  LOS signals do not have comparabile ground wave
> coverage area as 800 mhz. signals.  That's why you see more PCS towers.
> _______________________________________________