What is the Dual Capacity Direct Mode (DCDM)

What’s the Dual Capacity Direct Mode(DCDM)?

DCDM is Dual Capacity Direct Mode. It is a feature which allows two slot operation on simplex. Not only does it offer two slot operation but is also currently the only product which complies with ETSI TS102-361 §1-4 v2.1.1 for 6.25e operation on simplex.

Dual Capacity Direct Mode also is known as 6.25 kHz Equivalence Direct Mode (6.25e DM) – provides additional spectral efficiency by supporting up to two simultaneous Direct Radio-to-Radio Mode subscriber calls within a 12,5kHz allocation of spectrum.

Retevis has many radios has this feature, like Ailunce HD1, Retevis RT82, RT3S, RT83, and Mobile Radio Retevis RT90.

Price sensitive customers, migrating from Analogue to Digital (TDMA) can move up to two talk paths, with 6.25e Direct Mode (TDMA), without a repeater. It also increases the total number of users supported on a 12.5 kHz channel with no degradation in performance.

How to turn on the CDCM on RT82 software and Ailunce HD1 software.

On RT82 software, you can check DCDM Switch in channel information.

On Ailunce HD1 software, We can set the work mode, Double Slot means DCDM, when you check it, just like you turn on the function.

What DCDM can achieve?

We know that the time slot does not work in simplex mode. Such as if all the parameters are the same only the time slot is different. we don’t turn on the DCDM, and we can communicate with each other in simplex mode.

For example:

Radio A: Tx=Rx=135.23750MHz, CC:1, Contacts: TG9, Time Slot:1

Radio B: Tx=Rx=135.23750MHz, CC:1, Contacts: TG9, Time Slot:2

Radio A and Radio B can communicate with each other. the time slot doesn’t work.

When we turn on the DCDM function, the time slot will work. If the time slot is different, they will can’t communicate with each other.

For example:

Make sure the radios have checked the DCDM function first.

Radio A: Tx=Rx=135.23750MHz, CC:1, Contacts: TG9, Time Slot:1

Radio B: Tx=Rx=135.23750MHz, CC:1, Contacts: TG9, Time Slot:2

Radio C: Tx=Rx=135.23750MHz, CC:1, Contacts: TG9, Time Slot:2

Radio A and Radio B can’t communicate with each other. Radio C and Radio C can communicate with each other. The time slot work when checking the DCDM. Only the time slot is same, they can communicate with each other.