MTR2000 DPL Early Talk-Off

[Birken Vogt]

We have some MTR2000s that the field radios are having a hard time decoding the DPL. Sometimes several seconds before the speaker will unmute. A carrier squelch radio hears it perfectly. No changes to the system in a year or more. Did the deviation alignment. Pattern looks good on the spectrum analyzer to the eye but deviation is a bit low in the mid-200s. I gather this cannot really be changed. Is some component going bad? Is this even possible? We temporarily replaced the transmitter with a TK-790 and a CPI tone panel and it works much better. Mobile radios are a mix of various ages of high tier Motorolas and some Kenwoods.

[Bill_G]

You will have to do the xmit dev alignment again. You want the PL dev to land near 500hz. The PL to Voice deviation relationship is fixed. You can't adjust it, and you can't adjust their levels independently. If DPL is low, then voice is low too. And MTR2K's are notorious for low dev.

Do the dev procedure again across all freqs, and then recheck DPL/Voice levels on your freq of interest. If still too low, subtract 100 hz from the values you entered, recheck freq of interest, and repeat until the levels are correct.

Once better dev is reached, if subscriber units still have a tough time decoding, then you have a failure you might not be able to fix yourself. You'll probably have to replace the RF section in the center.

[Birken Vogt]

We are contemplating switching the whole system to regular PL. We don't know any other sizable public safety customers using DPL. Nobody ever seems to have much trouble with PL it seems, but DPL seems an unnecessary complication. And even when everything is working right it is still slower to decode and less reliable in case of interference or twist.

[Bill_G]

DPL is great in congested service areas with a lot of cochannel users. But, if you don't have a problem with busy channels, then the advantage of numerous available codes disappears.