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Motorola channel assignment for rebanded systems

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gmclam

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I have a chart here which shows the frequency assignments in a Motorola trunked system, from channels 001 to 920. Is there such a chart for rebanded channels? Are only channels 440 to 559 affected by rebanding?

I thought a larger portion of the spectrum was being "moved", but channels 440 to 559 only indicate it would be from 861.9875 to 864.9625. Can someone clarify this for me?

Thanks.
 

dougr1252

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The data I have shows channel numbers starting at 0, up to 1022. You can make a chart yourself just by using the formula for each group of channels. This is what a scanner uses to figure out what freq to tune to. Once rebanding is finally done, most PS systems will only use the first 2 tables.

0 = 851.0125
+ .025
439 = 861.9875

"Rebanded" 440-559
440 = 851.0250
+ .025
559 = 854.0000

"Old" 440-559
440 = 862.0125
+ .025
559 = 864.9875

560 = 865.0125
+ .025
719 = 868.9875

720 = 866.0000
+ .025
759 = 866.9750

815 = 867.0000
+ .025
831 = 867.4000

958 = 868.9750

961 = 867.4250
+ .025
1022 = 868.9500
 

WayneH

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You don't need to post a table. It's pretty clear what changed and how to identify the rebanded channels. First, what was moved and all the talk is completely separate from what Motorola did to accompany the changes is band assignment. Since the standard channel identifiers for 851-854 are for 25kHz spacing Motorola had to reassign a range, a range no longer needed upon rebanding, to be used to create more channels within the 851-854 sub-band to create an equivalent 12.5kHz spaced range similar to 866-869.

So anything between 851 and 854 that ends in zero is a rebanded channel and has a new identifier. Example: 852.3000, 853.6750. Anything like 851.###0.
 

gmclam

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I'd like to be able to look at any Motorola system in the database, and from the frequencies listed, be able to know beforehand whether or not the system can be properly trunk tracked on older (PRO-95 & PRO-97) scanners.

Now that I have the formulas the scanners are using to make the calculations, it seems easier to have a chart with the 'problem' frequencies highlighted. If any of those frequencies are used, it won't track properly.

Also, it sounds like there is a fairly generic setup for newer scanners (such as PSR-300) to track these rebanded systems by programming a custom map. It seems like that custom map should work on all rebanded systems that are using this new voice channel formula, and not have to be different for every system out there.
 

WayneH

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I'd like to be able to look at any Motorola system in the database, and from the frequencies listed, be able to know beforehand whether or not the system can be properly trunk tracked on older (PRO-95 & PRO-97) scanners.
It sounds more like you want to do it the long way for the sake of doing it. Otherwise use the info I gave you. It's very simple and you don't need a table to look at.

851.0125 Old assignment
851.0250 Rebanded assignment
851.0375 Old
851.0500 Rebanded
And on and on....

If there's a 5 at the right-most then it's the older assignment. If it's zero, then it's a rebanded freq.
 

gmclam

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Rebanded Motorola channel numbers

It sounds more like you want to do it the long way for the sake of doing it.
Actually I do. It is one way to have greater memory retention of the information.

I understand the original Motorola concept - transmitting channel numbers, and the fact receivers use a forumla to calculate the voice channel. Information on rebanding tends to be (over)simplified and/or missing information. The idea is clear - frequencies in a section of the band are being vacated by public safety, and "new" channels will take their place. But seeing all this information without having to search out all the parts has been tough. And I want technical info, not info that has been simplified for consumer consumption.

Otherwise use the info I gave you. It's very simple and you don't need a table to look at.
A picture is worth 1000 words. Seeing a chart of either the frequencies or the channels will be far more clear and easy to identify than looking a frequencies per se.

851.0125 Old assignment
851.0250 Rebanded assignment
851.0375 Old
851.0500 Rebanded
And on and on....
That looks good in theory, but then people go an add zeros to the end of frequencies. For years I knew the local CHP frequency was 42.20 MHz (that's what is stamped on my crystals). Then my first programmable scanner displays 42.200. The next one shows 42.2000. The latest one shows 42.20000 MHz.

For example, take a look at the frequencies in this rebanded system: Scanner Frequencies: Bowling Green-Warren County Public Safety Trunking System, Bowling Green, Kentucky

ALL of the frequencies end in zero, which would make one think that this can not be scanned by a PRO-95, PRO-97, etc. But that is not true, as the channels/frequencies are the same as original vs rebanded in the chart.

If there's a 5 at the right-most then it's the older assignment. If it's zero, then it's a rebanded freq.
It depends on how many zeroes are added to the frequency, as shown above.
 

gmclam

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Motorola Channel Assignment Table

I created the table. I now realize that when rebanding is 100% complete, the tables required by our scanners will be much simpler. The max channel will be 559 and the max frequency will be 860.9875.

Thank you dougr1252; your email did not readily make sense to me, but once I got the table going it clarified the information.
 

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JBuff27

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25 kHz vs 12.5 kHz Spacing

Do I understand correctly that with the rebanding the use of 12.5 spacing is only temporary and will go away and that therefore some systems will go thru two rebanding to get to the final end point.

Thanks for any input on this since I am just now trying to figure out whats happening day to day as what I am hearing or NOT hearing keeps changing.

jbuff27
 

gmclam

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jbuff27, it is my understanding that the spacing will be as I have indicated. They used 12.5kHz spacing to get more channels in less spectrum. As I understand it, any specific system (or area) will not have channels that close (they will be 25kHz), but adjacent areas will essentially be interleaved at 12.5kHz.

One thing doing the chart made me realize is that we are losing a lot of channels from this change.
 

WayneH

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The PDF is all correct. The tables that are in use now are the permanent ones though once 866 is vacated the ranges for it can be removed further simplifying things. And you aren't really losing much when you consider Nextel will not be mixed in.

I'm still not sure why you need to print every freq out to figure out what's rebanded.
 
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gmclam

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The PDF is all correct. The tables that are in use now are the permanent ones though once 866 is vacated the ranges for it can be removed further simplifying things. And you aren't really losing much when you consider Nextel will not be mixed in.
Yes, once everyone everywhere is fully rebanded, that chart will be much simpler. In the meantime it is quite a mess.

I'm still not sure why you need to print every freq out to figure out what's rebanded.
It is not an issue of what is rebanded, it is an issue of whether or not an older scanner such as the PRO-97 will correctly trunk track an entire sysyem. My experiment down in Fairfield showed me that only 2 frequencies/channels did not track correctly. There will be fully rebanded systems that will properly track on the older scanners. And the problem with just looking at the last digit is that frequencies like 851.775 ends in 5, but 851.7750 does not. And 851.01250 also ends in zero. In other words, it is not the LAST digit that matters, but the position of that 0 or 5 that indicates if the channel can be found by older firmware.
 

WayneH

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And the problem with just looking at the last digit is that frequencies like 851.775 ends in 5, but 851.7750 does not. And 851.01250 also ends in zero. In other words, it is not the LAST digit that matters, but the position of that 0 or 5 that indicates if the channel can be found by older firmware.
If you explicitly tell someone to take it out to four decimal places then it works perfectly well; no list needed.
 

JBuff27

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Post #8-Motorola Channel Table

In trying to get a handle on a problem here in the East I am cross checking my listings with your Assignment Table and have a question. Please look at Channel 720 Vs 719, 868 vs 866, there seems to be a disconnect.
Also Ch 958 looks like it should not be there, if so where?

Thank you,

JBuff27
 

gmclam

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I re-read this thread and a couple of others related to this issue. It seems that posts are not explicit enough to get a point across. For people that already know the information, of course the posts make sense. But for someone trying to CLEARLY understand the total scope of the situation, the information provided is not clear.

By going through the exercise of creating a table, it pointed out to me which 'channels' are being changed, which are no longer being used, and how the spectrum is being divided. Certainly NOW that I see the table and re-read the posts it makes sense. It did not the first time.

While 851.###0 does in fact indicate that you carry the frequency out 4 places past the decimal point, that fact was not clear when I initially read it. Just saying that the frequency ends in a 0 is not good enough. dougr1252's post didn't make complete sense to me at first either, but certainly added up perfectly when comparing the post to the table. As I said, a picture is worth 1000 words.

Please look at Channel 720 Vs 719, 868 vs 866, there seems to be a disconnect. Also Ch 958 looks like it should not be there, if so where?
One thing of note, some people ID the first channel as 0, while others ID it as channel 1. I am looking at this from a technical level, so you might need to add 1 to every channel number. Perhaps that is your disconnect between 719 & 720.

I was surprised to see that there were a lot of unused higher channel numbers. It took some digging to get to this point, and there certainly could be errors in the high channel numbers. If you have information that shows something different, please provide the source of your info. My goal here was to get a table that I can use on rebanded systems; so channels above 559 weren't the priority.
 

WayneH

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I was surprised to see that there were a lot of unused higher channel numbers. It took some digging to get to this point, and there certainly could be errors in the high channel numbers. If you have information that shows something different, please provide the source of your info. My goal here was to get a table that I can use on rebanded systems; so channels above 559 weren't the priority.
The Motorola signaling word (or OSW) is broken down in to a command (or "opcode"), a destination (individual or group) and an address. What appears in the command portion determines what the address means.

To make a long story short, the reason there are various gaps is because the value used to represent a frequency is placed in the command portion of the OSW. Since 866 was a later add to Motorola trunking Motorola had to find unused commands to assign to the 866-869MHz range.

Sorry I continued to question you but it can be difficult to determine one's perspective on technical manner sometimes.
 

gmclam

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Motorola Channel Numbers in Frequency Order

The Motorola signaling word (or OSW) is broken down in to a command (or "opcode"), a destination (individual or group) and an address. What appears in the command portion determines what the address means.

To make a long story short, the reason there are various gaps is because the value used to represent a frequency is placed in the command portion of the OSW. Since 866 was a later add to Motorola trunking Motorola had to find unused commands to assign to the 866-869MHz range.
What I was actually looking for at first were the exact equations used by scanners to calculate the voice frequencies. I expected there'd be 3 equations; one for standard, one for splinter and one for rebanded. I did not realize the band or channel assigments were so segmented.

What go me going on this was a post in the Solano Co CA portion of the DB for a custom table to monitor their 800 MHz rebanded system. When I further tried to receive that system with a PRO-97, I wanted to understand EXACTLY the math being used by the firmware. Keep in mind, I write firmware (usually very low level) for a living.

In trying to help new members I ran into other systems posted here that were also rebanded. The issue came up whether or not they could be monitored by a PRO-95 or PRO-97. The mentality that has been used for the past several years is that these scanners will NOT work on rebanded systems. That statement is not entirely true because it depends on the specific frequencies a rebanded system uses.

For my next step, I sorted the table in FREQUENCY order. This left 3 possible channel numbers for each frequency. This looks at things from yet another perspective.
 

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WayneH

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The mentality that has been used for the past several years is that these scanners will NOT work on rebanded systems. That statement is not entirely true because it depends on the specific frequencies a rebanded system uses.
Any time this topic has come up and I've seen it I've expressed the same thing. If people are still ignorant, or poor information is being passed, I don't know what to tell you. It's been more than four months since I released the tables. People will believe whatever they want; or in the case of RR just post F.U.D..

With splinter systems there's no math involved. Freqs are just shifted down 12.5kHz after the standard calculations are done for anything between 856-866 (pre-rebanding).

For my next step, I sorted the table in FREQUENCY order. This left 3 possible channel numbers for each frequency. This looks at things from yet another perspective.
Splinter versus standard is determined by the radio's programming. Rebanding status is announced over the control channel.
 
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gmclam

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It's been more than four months since I released the tables. People will believe whatever they want; or in the case of RR just post F.U.D..
You released tables? Are they posted here? Can you point me to them? Thanks.
 

WayneH

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They're Stickies in the RadioShack and GRE forums. There are also links to them in some of the rebanding threads in other forums.
 
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