Motorola Radio on a Tait Tier 3 network

I'm trying to register a Motorola Radio on a Tait Tier 3 network. I am in control over this network, it only consists of one base station with two RF channels. So far I found all that is required, just one open question.

Motorola requires a network ID, 0-511 in the "tiny network" config that is used, and I can't find this in the Tait setup. Tait uses the MPT numbering, e.g. 200 2001 21, calculating the normal DMR ID is quite simple then, the result is 3 in this example.

Some vendors have the option of using a MPT1343 numbering scheme on DMR Tier 3. There is more information about MPT1343 numbering on DMR in this post.

The network size field in the system set, defines the DMR Location Area value. This value in turn determines how many bits can be used for the Network ID. The theory being, that there would be many tiny networks within the same frequency range; yet only a small number of huge networks, in any geographical area. In other words, the more bits you have for DMRLA, the higher the maximum site number can be. This is something that was also borrowed from MPT1327. There is more information about the Network ID and DMRLA in this post.

I don't have access to any Tait technical information but I believe they call Network ID, DMR Network Code. DMR LA and Network Model have the same name as far as I can tell.

Some others things which may help:

• Turn off Talkgroup Subscription.
• Make sure that System Type is set to Capacity Max Open Radio. 
• Location Area bits needs to be the same as any Tait (or other) radios on the network - or the maximum allowed according to the Network Model.
• The site number (Site ID) in the radio must match the system's site numbering. This should be 1 but you might have it set differently.

All of these are in the system set. Be aware that only some features have been tested and are known to work in this scenario.

And second question, when I make the channel plan, is the repeater shift 10 or -10 MHz, when using downlink 420 and uplink 410 MHz for the base station?

DMR Tier 3 allows for two types of channel plan:

A fixed or standard channel plan. This would be used when the system frequencies have the same TX-RX separation. The standard channel plan makes use of a Base Frequency - which is the mathematical channel one - and all frequency pairs are represented as channel numbers (Physical Channel ID) based on the step size.

MOTOTRBO radios and repeaters allow for up four Segments with up to 4094 channels in total. Each Segment can use different TX-RX spacings - this means that not all the channels have to have the same TX-RX spacing. Here is an example of how this would work.

A flexible channel plan. This would be used when none of the frequencies have the same TX-RX separation. You would find this a lot when a customer had an analogue system or two or more companies merged and they kept their existing frequency allocations.

MOTOTRBO Capacity Max allows you to use both the standard and flexible channel plans but you need to make sure that there is no channel number conflict between the two - if you will use both. You will also get a warning (not an error) in Radio Management.

For each Segment in the Fixed Channel Plan, there are five fields:

Enable. This enables the segment and tells the radio to use the frequencies defined here.

Number of Channels. This defines the number of channels in that segment. For example, if all four Segments were enabled, and the Number of Channels was set to 1023 in each, then the channels for segment 1 would be 1 to 1023; segment 2 would be 1024 to 2047; segment 3 would be 2048 to 3071 and segment 4 would be 3072 to 4094. The sum of number of channels cannot exceed 4094 so segment 4 would be slightly smaller.

Frequency Duplex Split. The TX-RX separation for this specific segment. Since you can have up to four segments, you can have up to four variants on TX-RX split. A positive value means that the repeater TX frequency is above the radio TX frequency (the value shown in this field). Entering a negative value reverses this. The valid range for this field is -50 to +50MHz. I have given some possible examples in this table.

Subscriber Transmit Frequency Base (MHz). As the name suggests, this is the radio transmit frequency on mathematical channel one (sometimes called Base TX Frequency)

Frequency Separation (kHz). This is the step size for the channel numbers from the Subscriber Transmit Frequency Base (MHz). One can choose 25kHz but all frequency allocations are 12,5kHz nowadays.

In the Flexible Channel Plan you simply would enter channel numbers and frequency pairs. The channel number (Physical Channel ID) must not be in the range used by any segment in the Fixed Channel Plan.

You can find out more about how channel numbers work in DMR Tier 3 here.