[TrunkCom] Control Frequency Only Mode

[Tom Swisher]

JERRY NONE wrote:
> You well aren't the LCN channels? As in Logic Channels?
> I am a little confused here.
> MOTO has a band plan channel and EDACS and LTR have
> Logic Channels?  What is the difference?

Motorola systems assign 800 and 900 MHz frequencies based on the channel 
number assigned each frequency by the FCC. EDACS and LTR channel numbers 
are assigned in the system itself: 1, 2, 3, 4 and so on.

When a Motorola controller makes a channel assignment, it tells the 
radio "go to channel 607". The radio has a table of frequencies in it's 
firmware and knows from that what frequency to use. Thus, Motorola 
radios only need the control channel frequencies for a system, so that 
they know where to listen for control data. The same is true for more 
recent scanners, which have the same channel table in their firmware.

Channel numbers for EDACS and LTR, on the other hand, are defined on a 
system-by-system basis. It's entirely up to how the person who set the 
system up was feeling that day; this is why the Logical Channel Number 
arrangement in some systems goes up in ascending order by frequency, 
while others jump all over the place.

Thus, EDACS and LTR controllers tell radios "go to channel 3", and the 
radio goes to channel 3, the frequency for which was defined in the 
radio itself when it was programmed. EDACS and LTR radios therefore do 
not have a pre-defined table of frequencies in them, just what has been 
defined for the system itself.

And this is where the problem lies with rebanding for Motorola and 
scanners; the frequencies between 851 and 854 MHz are currently 
channelized at 25kHz steps, for a total of 120 channels. With rebanding, 
that segment of the band is being rechanneled at 12.5kHz steps, which 
will give 240 channels. However, rechanneling means the channel numbers 
will change, and some older Motorola radios (and scanners) are not 
capable of having their firmware upgraded for the new channel tables and 
thus won't work if a system is rebanded to 851-854 MHz. EDACS and LTR 
systems won't have this problem since they are manually defined.

However, a likely workaround for some older scanners will be to simply 
define a custom channel table for the 851-854 band, using 851.0125 as a 
base and 12.5kHz as an offset.

Tom WA8PYR
--
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Tom Swisher, WA8PYR         wa8pyr-scan at sbcglobal.net
  "Restriction of free thought and free speech is the
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        WA8PYR Radio - http://www.wa8pyr.net