[TrunkCom] Control Frequency Only Mode

Wed Oct 26 20:53:17 EDT 2005

Basically, Motorola uses an "absolute" channel number, and EDACS and LTR use
a "relative" one.

In Motorola systems, there is a base frequency (something like 850.0000) and
a "step" (say 0.0125)  Any frequency that could possibly be used can then be
expressed mathematically as base + (step * channel).  What will break the
scanners with the rebanding is if they change the base (say to 840.0000).
The control channel says the same thing (go to 500 translates to go to
850.0000 + (500 * 0.0125) or 856.250.  If they change the base to 840, then
"go to 500" means go to 846.250, and the old scanner still goes to 856,
instead of 846.

In EDACS, the control channel says "go to SLOT 3" (I used slot intentionally
to avoid confusion - the computer really does it in binary so the term used
doesn't matter).  The radio (user's) interprets that as "go to memory 3".
The scanner handles that by going to "the channel in this bank ending in
'03'".  So it always works, as long as the right frequency is stored in
memory x03.  If they change the freqs used by the system, you just reprogram
the memories to match.  But that's also why the LCN order matters.  If LCN 1
is 856.0125 and LCN 2 is 857.0125, if you reverse them, you always go to the
wrong frequency.  The scanner goes where the control channel data told it to
go - but the call it expected wasn't there.

HTH,

Jay

-----Original Message-----
From: trunkcom-bounces at mailman.qth.net
[mailto:trunkcom-bounces at mailman.qth.net] On Behalf Of JERRY NONE
Sent: Wednesday, October 26, 2005 13:05
To: Discussion of Monitoring Trunk Radio Systems
Subject: RE: [TrunkCom] Control Frequency Only Mode

So then why don't we need the L.C.N.s or Channel Numbers for Motorola but we
need them for EDACS and LTR?

--- bearcat <rwnewbould at comcast.net> wrote:

> Each 800/900 mhz freq has been aasigned a channel no.  The control 
> channel data from the system tells the units which channel no. (hence
> freq) to go to.  The scanner gets the information from the system 
> control channel so they can add as many new sites as they need and the 
> data will then be on the system control channel so the scanner handles 
> if just fine.  This is why rebanding is such and issue the channel 
> no.s being sent will make no sense to the scanner.  The advantage to 
> using CC only programming is that if something would change on the 
> system the scanner user will never miss a beat.  If you have all of 
> the freqs programmed in a a new site is added you will not hear it.
> 
> This is explained to the best of my limited tech knowledge
> 
> Rich
> 
> -----Original Message-----
> From: trunkcom-bounces at mailman.qth.net 
> [mailto:trunkcom-bounces at mailman.qth.net] On Behalf Of JERRY NONE
> Sent: Monday, October 24, 2005 10:58 AM
> To: Discussion of Monitoring Trunk Radio Systems
> Subject: Re: [TrunkCom] Control Frequency Only Mode
> 
> 
> Does anybody have a copy of this band plan?
> 
> --- Jeff Kenyon <at649 at tcnet.org> wrote:
> 
> > Hi Jerry, a scanner that doesn't support control only mode will have 
> > the frequencies as reference to go to for a transmission.  In 
> > control channel only mode, the scanner follows the specific band 
> > plan that Motorola has set up for its various bands such as 800 and 
> > 900
> MHz
> > trunking so that is
> > how this is all possible, and with control only
> mode
> > you can hear all the
> > transmission, and any subsequent transmission.
> > 
> > 
> > 
> > 
> > 
> > On Mon, 24 Oct 2005, JERRY NONE wrote:
> > 
> > > Question.  Okay, say for instance you have a
> radio
> > > scanner that does NOT do Control Frequency Only
> > Mode.
> > > So you program in all the frequencies.  So when
> > the
> > > Controller tells Talk group 336 to go to a
> > frequency
> > > of 868.7125, how does a radio scanner in Control Frequency Only 
> > > Mode know NOT to go that
> frequency.
> > > Instead the message is heard on one of the
> Control Frequencies.  
> > > Also by being in Control Only Mode,
> > does
> > > this prevent the radio scanner from hearing all
> > the
> > > transmissions?  I mean if the system you are monitoring has seven 
> > > frequencies and then adds
> > three
> > > more frequencies to accomodate extra users but
> the
> > > Control Frequencies remain @ the same amount,
> > won't
> > > that cut off some transmissions?  What happens
> > then,
> > > do you just hear the priority transmisions?
> > >
> > >
> >
>
========================================================================
> > > County Of Medina Ohio County Scanner Group: 
> > > http://groups.yahoo.com/group/medinascanner/
> > >
> >
>
------------------------------------------------------------------------
> > > Southwest_Parma_Strongsville Scanner Group:
> > >
> >
>
http://groups.yahoo.com/group/Southwest_Parma_Strongsville/
> > >
> >
>
------------------------------------------------------------------------
> > > There will be a new radio scanner on the market
> > soon.  Here is the Yahoo Group for that Radio
> > Scanner:  http://groups.yahoo.com/group/BCD996T/
> > >
> >
>
========================================================================
> > >
> > >
> > >
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> 
>
========================================================================
> Southwestern Cuyahoga County Ohio, Parma Ohio & Strongsville Ohio 
> Radio Scanner Group:
>
http://groups.yahoo.com/group/Southwest_Parma_Strongsville/
>
------------------------------------------------------------------------
> County Of Medina Ohio County Scanner Group:  
> http://groups.yahoo.com/group/medinascanner/
>
========================================================================
> 
> 
> 		
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========================================================================
Southwestern Cuyahoga County Ohio, Parma Ohio & Strongsville Ohio Radio
Scanner Group:
http://groups.yahoo.com/group/Southwest_Parma_Strongsville/
------------------------------------------------------------------------
County Of Medina Ohio County Scanner Group:  
http://groups.yahoo.com/group/medinascanner/
========================================================================

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