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Thread: Audio imbalance with Moto and Vertex

  1. #1
    PRC148 No Longer Registered

    Default Audio imbalance with Moto and Vertex

    In my area the Sheriff uses HT1250 portables and CM300 mobiles. The PD uses HT1250s and Vertex VX4000V mobiles.

    The dispatch center uses a CDM750 for control station link from dispatch to a voting Motorola system on the Sheriff side. The PD side is a Vertex VX2000 to a VX7000 repeater.

    When we narrow banded the Sheriff enabled full compression and expiation. However the PDs VX4000V mobiles do not have that option although the software indicates they should.

    The Sheriff's users complain of low audio when scanning the PD frequency. I'm trying to come up with the best option here. I cranked the VX4000Vs up as much as possible but I'm assuming the lack of compression is what's causing the lower audio on the Sheriff's side.

    Does it seem reasonable to go to the PD repeater and adjust the modulation output up a bit there as a work around?

    Is this a normal consequence of the differing audio processing settings between the two brands?


  2. #2
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    I'd try turning off the compression and seeing how it sounds. Motorola's commanding does't play we'll with others.

  3. #3
    PRC148 No Longer Registered

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    I should have added, turning off the Sheriff's compression is not much of an option but might end up being one in the end. Being two separate Gov entities they don't always play well together and want the other to find the solution. I have far easier access to the PD equipment and there are far fewer mobiles to deal with than on the Sheriff's side. I'm hoping to find a way to deal with this on the PD side mainly.

    Does the compression on one side and lack of compression on another tend to cause that difference in audio levels?

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    I know some Vertex radios had issues with faulty narrow filters, you might also want to check into that. I know my old employer has been replacing filter in some of the vertex radios primarily the VX2200's and some others.

  5. #5
    PRC148 No Longer Registered

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    What kind of filter issues? What were the symptoms?

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    Quote Originally Posted by PRC148 View Post
    What kind of filter issues? What were the symptoms?
    IIRC Just filters going bad and when they did you would get low volume on Narrow Band freqs. Tomorrow I will call him and ask him exactly what the problem is. They are still replacing filters and Vertex is paying them half hour labor to replace the filters them selfs.

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    Does the sheriff's voting system use a MTR2000? If you look at the wireline tuning instructions for the MTR no matter what level you set the wireline to you will get 60% full system deviation. If you change the mod level from 2.5 to 4.0 60% of 4 is 2.4. Very few users ever talk into their radios properly to drive full deviation.

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    Quote Originally Posted by JMINN699 View Post
    Does the sheriff's voting system use a MTR2000? If you look at the wireline tuning instructions for the MTR no matter what level you set the wireline to you will get 60% full system deviation. If you change the mod level from 2.5 to 4.0 60% of 4 is 2.4. Very few users ever talk into their radios properly to drive full deviation.
    My god please tell me you are not advising them to set the base station for 4k deviation when they are only licensed for 2.5k. And that info about the MTR is completely false. I have worked on many MTR's since they were released, when you set the wireline deviation you inject a tone at the level you want to be 60% deviation. If you have a voting system as suggested, you inject a 1k tone over the air to a tac rx at 60% then measure the level coming into the transmitter. If you want 1:1 then you inject a 1k tone at this level into the mtr during the aligment procedure, if you want a 3db boost then inject the level you measured -3dbm
    "Don't worry about what I am, cause I'm a state agent so what you need to do is make sure your doing the right thing **** boy" -J. Dewitte

  9. #9
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    I have bench tested this on several MTR's. 60% deviation is all they will put out from the wireline. You tell it what level you want for 60% system deviation and that is what it gives you, increasing the wire line level above this point will only cause clipping, so nomatter what level you set for wireline you get 60% full system deviation. At 60% full deviation will only be 1.5kc. This is not true of repeater level. Since we are talking about a voter system, then it should only be set up for wireline.