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Thread: CDM1250 Vhf missing transmissions

  1. #1
    PRC148 No Longer Registered

    Default CDM1250 Vhf missing transmissions

    We have several Vhf CDM12250s in service. The other half of the fleet are VX4000V mobiles. The repeater is a Vertex/Motorola VX7000.

    I've received complaints of the CDM1250s missing transmissions. I use a W3 Astro Spectra so I don't often get a chance to see this CDM issue but today I saw it myself. We were scanning and the LEDs would indicate activity but the radio would not unmute, even on the main priority mode. I tried placing the radio in monitor mode but id didn't make any difference. I've been told by a local shop that the VX7000 could be producing low PL deviation after narrowbanding which could cause the CDM series to miss a valid transmission. Does this sound correct? Has anyone else heard of this issue with the CDM series? The VX4000Vs are rock solid and never miss a transmission regardless of the PL state.

    We have them set to full expansion and compression. The codeplugs are virtually identical as the HT1250s in service and they never experience this issue.


  2. #2
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    We have CDM1250's and 1550's on MTR2000 repeater narrow banded and don't have any problems. I believe Motorola' s companding to be evil and should be destroyed. It really doesn't play we'll with others. Try turning off the companding

  3. #3
    PRC148 No Longer Registered

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    I know. It sounds like securenet to me with the grainy low quality audio. What confused me was the fact monitor mode did not appear to make a difference. Wouldn't the selection of monitor mode defeat the PL Scan Type: Priority - Non Priority selection in the scan list field?

    I will try disabling the expansion and I might go over and bump up the PL level on the repeater a tad bit.

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    Verify that Selected channel is in the scan list. We have had several CDM1250's that for some reason will fail to unmute on the selected channel while in scan but will show that there is activity their. All of the units have not had "selected" in the scan list. However we also have units that do not have "selected" in the scan list that work fine, it seems to only affect certain units, not sure if its a failure or a firmware bug.

  5. #5
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    If you have PL lock out checked, monitor wouldn`t make a difference. The radio would have to be able to decode PL in order to lock on channel when in scan.

  6. #6
    PRC148 No Longer Registered

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    Selected is in the list however PL lockout was selected. I deselected that and now it appears to be working properly.

    Thanks for the help.

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    Is it missing the entire transmission or just the begining. We found that the DOS setting was muting the radio for 1/2 sec before the audio was heard. Try turning off DOS.

  8. #8
    PRC148 No Longer Registered

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    It was missing entire transmissions. Our MDC is post so DOS didn't seem to be an issue. I unchecked PL SCAN LOCKOUT and that seemed to clear things up nicely so far.

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    Quote Originally Posted by PRC148 View Post
    It was missing entire transmissions. Our MDC is post so DOS didn't seem to be an issue. I unchecked PL SCAN LOCKOUT and that seemed to clear things up nicely so far.
    It didn't matter whether the MDC is post or pre, the DOS mutes the receive audio for 1/2 second

  10. #10
    PRC148 No Longer Registered

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    Oh, I didn't realize that. I will try that too. Thanks.