Colour Code?

In digital mode, all MOTOTRBO radios support a feature known as Color Code (USA: Color, everywhere else: Colour). In fact this is defined in the ETSI DMR standard.

In a MOTOTRBO radio or repeater, there is a color code field which allows the selection of one of 15 colour codes. A radio which has been programmed with colour code 1 will not be able to transmit on a repeater configured with colour code 2 and so forth. A radio can be configured with multiple colour codes - one for each channel. A repeater can only be configured with one colour code.

Colour code is useful because it can prevent radios from one site or system mistakenly roaming to another site or system which uses the same frequencies. Although there is activity from the neighboring system, the radio will ignore all transmissions from the other system because it has a different colour code.

This is also useful for telecommunication regulators who have to allocate the same frequency to two DMR licencees in the same region. The regulator simply has to specify a colour code in the licence conditions - much like PL/DPL was used in analogue as a guard tone.

There is a limitation of course, if two geographically adjacent radio systems use the same frequencies, yet use a different colour code, there will be audio quality issues in the area where radio users are able to receive signals from both systems at roughly the same signal strength.

MOTOTRBO radios can also be configured to be "polite" to other systems using the same frequency. In the CPS, it is possible to set the TX Admit Criteria to be Color Code Free. This will only permit the radio to transmit if there is no signal, or if the signal present on the receive frequency has the same colour code.

On simplex channels which employ DCDM, colour code 15 is reserved for inter-radio synchronization signaling - so only 0 to 14 may be used on systems that use this feature.

Although not intended for this, colour code also provides an additional mechanism to prevent casual eavesdroppers. More determined (resolute) eavesdroppers will however be able to determine the colour code using a scanner and a decoder application. In such cases Enhanced Privacy or 256 bit AES should be used.

9 comments:

  1. Hi Wayne. A small question. Is there any way to have a permanent transmission from the DR3000 (for couple hours) in order to realize a survey.
    Regards.

    ReplyDelete
  2. That is possible in analogue mode: a jumper between PTT and ground will get the repeater to transmit. You will also need to set the TOT to infinity.

    In digital mode this is a little difficult to do.

    ReplyDelete
  3. Hello Wayne, please share from your experience. 5 DMR(MOTOTRBO) repeaters at a single site using different color codes are working well for 10 channels. Tx freqs from repeaters go like 161, 161.2, 161.4 etc with 5MHz separation to Rx freqs in VHF band.Now , if the color code of the 5 repeaters are made same,what problems may come ?.please.

    ReplyDelete
  4. Hello Wayne, please share from your experience. 5 DMR(MOTOTRBO) repeaters at a single site using different color codes are working well for 10 channels. Tx freqs from repeaters go like 161, 161.2, 161.4 etc with 5MHz separation to Rx freqs in VHF band.Now , if the color code of the 5 repeaters are made same,what problems may come ?.please.

    ReplyDelete
  5. Hi Wayne,

    do you know how we read the repeater received signal strength from handsets?

    I remember the repeater will send the information to the requested handset
    via a code. I am using DP4800.



    tks

    ReplyDelete
    Replies
    1. No, that is not possible. You can get the radio to display the current RSSI - it's in the menu. There might be a 3rd Party Application (which I'm not aware of) that links into the repeater and is able to report back the inbound RSSI as a text message.

      There is a site survey tool from Motorola that can log RSSI and GPS but this is a PC application (Windows).

      Delete
  6. Is there any way to match the MOTOTRBO "DPL" code on a Technisonic TFM 500(aircraft radio) for communications between landmobile and aircraft? We've been working with these radio systems and aircraft/ ground crew connections for years, and all of a sudden...

    ReplyDelete
    Replies
    1. In analogue mode MOTOTRBO radios support DPL and will work with all other manufacturers equipment. A quick test on a Communications Analyser will verify this.

      Delete

Powered by Blogger.