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Store & Forward Repeaters in a Simplex System

Store and Forward Repeaters in a Trio Simplex Licensed Radio System

It does sometimes occur in a licensed 400 MHz system that only one radio frequency is available. How do you accomplish Store & Forward repeating in this scenario while ensuring the remote devices don't hear both the direct and repeated signal? And how about a situation where two or more repeaters are needed in series?

Here's how it will work in a system with two Store & Forward repeaters. (you can extrapolate from this example if you need more, or just one repeater) The Translate feature will be required in the two repeaters instead of Repeat, because otherwise you could end up with never-ending data ping pong. (1st repeater re-broadcasts a message, 2nd hears it and re-broadcasts it, 1st hears it again and rebroadcasts it again, etc)

Also, having a different Tx and Rx SID is critical in situations like this so even if a radio hears a message from a radio other than the radio directly adjacent it will ignore it. You do NOT want two copies of a message going out any radio's serial port!

The Store & Forward repeater may be either an ER450 or MR450 type. If a full duplex repeater is required (Tx and Rx at the same time) then only one repeater can exist at a time in the system. Instead, in such a case to extend the system two back-to-back radios will be required.

 The 
Carrier Detect Collision Avoidance feature MUST be enabled in all radios. (default slots & time per slot settings are usually fine) This ensures that if a radio hears someone else transmitting it will not also transmit, causing a collision.

The first few columns below are definitely required. The last two regarding diagnostics are optional, only used if the customer wants to be able to do remote diagnostics & programming from the SCADA Host site.

 

NOTE: If two or more repeaters exist in the system, do NOT enable Repeat Diagnostic Messages in the Diagnostic setup dialog. This should only be done if there is only one repeater! Instead the Translate feature will be used to pass diagnostic messages between sites.

If remote Diagnostics is to be performed, ensure that SID 10 is entered as the diagnostic stream ID for ALL radios in the TView+ Diagnostics database, NOT SID 0. This is because every radio will always respond to SID 0. (Intended as a "back door" for local diags) We thus do not want to use SID 0 when doing diagnostics through repeaters. If the destination remote were to hear both the direct message (using SID 0) and repeated message (using a higher translated SID) it could get confused.

In each radio's Diagnostics Setup dialog the From & To diagnostic Stream ID should be entered as noted in the table below, (10, 11 or 12) and in the two repeaters the noted translations of the diags SID must be added.

NOTE: Using the Translate feature will also assist in systems where only ONE repeater exists, but some remote sites are also communicating directly with the master site radio.

  Port A TX SID Port A Rx SID User Data Translate Diags SID To/From Diagnostic Translate
Host Site 1 2 N/A 10/10 N/A
Local Remotes 2 1 N/A 10/10 N/A
Repeater 1 2 1 1 to 3 10/10 10 to 11
      4 to 2   11 to 10
Repeater 1 Remotes 4 3 N/A 11/11 N/A
Repeater 2 4 3 3 to 5 11/11 11 to 12
      6 to 4   12 to 11
Repeater 2 Remotes 6 5 N/A 12/12 N/A


 











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So if remote diagnostics is not included there must be two (2) translate entries in each of the repeaters. If remote diags IS desired there will be four (4) translate entries!

NOTE: In order to enable the Repeat/Translate feature in an E Series radio one of the serial ports must be disabled. (typically port B)

The concept demonstrated above can be extended to include three or more in-series repeaters. It can also be extended to create separate branches for parallel repeaters. The common repeater would use one set of SID's but repeaters beyond in each branch would then diverge to use separate SID's.

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