Subject: [NEXTEL-1] Re: 700/800 Trunking

From: "John Marcel" <[email-masked]>
Date: Thu, 15 Jul 2004 08:27:26 -0400

We have three trunked systems in this area (one EDACS analog High-Band, one
EDACS analog/aegis 800 & one Moto P25 800). Both 800 systems utilize simplex
frequencies in a cross-channel system to access whatever talkgroup has been
assigned for fireground operations. This is due to coverage issues and
simply the fact that a firefighter in a building talking a couple hundred
feet to his pump operator really doesn't need to talk to a hilltop or
high-rise repeater.

I suppose if choosing a system, P-25 is an important factor to consider
since it has become the US standard. However, if designed right, any system
can be setup for interoperability. The system here on P-25 Moto has full
Mutual Aid interoperability simply because they kept & maintain their old
VHF High-Band analog system which is used by all the fire departments around
them. They patch the fireground 800 talkgroup to the High-Band fireground
and dispatch talkgroup to the High-Band dispatch channel. In addition, they
maintain High-Band mobiles/portables in all the apparatus.

The High-Band EDACS system is now used by the police & highway departments
and has been abandoned (for the most part) by the Fire Department. I believe
(not confirmed) they are no longer buying EDACS capable radios and are
simply back to using the Simplex channel they had w/some pac-rats &
additional remote receivers.

Here in New Hampshire P-25 digital has become all the rage toted as the
"Answer to Interoperability". We've had many up's and down's in NH and
what's shaken out of it is that digital can be a great tool, IF it's going
to be used for it's intended purposes. It was also easily determined that
digital signals just don't carry as far or as well as analog. The city's PD
where I work is P25 now and they required 7 sites for 95% coverage. They had
been using 3 sites earlier for 85-90% coverage in analog. It's harder for
radios (with or without the corrective software) to translate the 1's and
0's of digital over the airwaves. There is no gray area or scratchy signals
w/digital. It's either there or it isn't. However, the audio quality is
super clear when in a strong area of the system. If you're going to go
digital, look at all the data features, not just voice. Using it for just
voice is kind of silly since you can do that more reliably in analog. My
Fire Department has all P-25 radios but we use them in analog. We are
exploring some mixed mode data(p25)/voice(analog) ideas now.

Most importantly is listen to the end users. The firefighters, EMS
personnel, cops and anyone else that would use these radios everyday. They
are a far better source for a well designed system than all the chiefs and
administrators. Bring that information to a reputable consultant and make it
understood this is designed for what the end users want w/expansion
capability. Don't fall into the bells & whistles traps.

John Marcel/K1FDD
Concord, NH Fire Dispatch

----- Original Message ----- >
>       1. Re: 700/800 Trunking
>            From: [email-masked]
> ________________________________________________________________________
> ________________________________________________________________________
>
> Message: 1
>    Date: Thu, 15 Jul 2004 00:44:12 -0000
>    From: [email-masked]
> Subject: Re: 700/800 Trunking
>
> First thing to do is to secure a reputable consultant to give
> you the good, bad, and ugly of analog vs digital.
>
> As to coverage reliability, it's typicially medium density with 15dB
> loss.  Don't let them sell you on outdoor or light building coverage
> for the 95% reliability factor.  The end users will never let you
> hear the end of it.  How many square miles is the County?
>
> --- In [email-masked], NEXTEL-1 wrote:
> >
> > The county I am in is starting the process of
> > designing a 700-capable/800 trunking system
> > using primarily portables for about 1200 to
> > 1400 users.  There is an interesting internal
> > debate about analog vs. digital vs. P25 digital.
> > Some are insistent on P25, some want the spec
> > more open to allow for analog EDACS, etc.  The
> > features of digital vs. analog are debated,
> > especially for the fire service.  The amount of
> > loss allowed for in-building coverage is another
> > lively debate.
> >
> > Any thoughts from this group to add fuel to the fire?

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