Results 1 to 8 of 8

Thread: GM300/Maxtrac Narrowband Modification

  1. #1
    Alpha's Avatar
    Alpha is offline T S - Moderator
    CS Forums $upporter
    Join Date
    Feb 12, 2012
    Location
    Directly above the center of the earth.
    Posts
    2,780
    Thanks
    1,235
    Thanked 1,531 Times in 738 Posts
    Country: Christmas Island

    Default GM300/Maxtrac Narrowband Modification

    I installed several HLN9575 / HNL9576 GM300 Narrowband modification kits that were produced by Motorola. These were ordered by a friend who was told by Motorola that they were the last ones they had. These are not new, the included documentation says they are from June, 1995, so this conversion has been around since the radio models were new, this is not something that is a reaction to the recent narrowbanding mandate, but no doubt the scarcity of them now may have something to do with it...

    I don't know if they plan on making any more of them, so I thought I would document the procedure and parts that were used so that it could be replicated in case they no longer plan on making the modification kits available. The HLN9575 kit is for VHF radios and the HLN9576 kit is for UHF radios. The modification applies to GM300 and Maxtrac series radios.

    1 Overview.jpg

    The modification is documented with this instructions sheet that comes with the kit:

    6880904Z18-O HLN9575-6 GM300 Narrowband Kit.pdf

    This is my write-up of the modification, including step-by-step notes and pictures of the procedure:

    Motorola GM300 Narrowband Modification.pdf


  2. #2
    Will No Longer Registered

    Default

    Thank you, I may still have to do some of these some day, and now the information is in a good place.

    The filters work in Maratrac radios also.

  3. #3
    Join Date
    Jun 26, 2012
    Location
    New York
    Posts
    274
    Thanks
    53
    Thanked 48 Times in 24 Posts

    Default

    When I used to work for a radio shop my boss did these to a few gm300's and some maxtracs. From what I was told Motorola stopped making the kit due the FCC crying that the radios where not type accepted for narrowband.

  4. #4
    Alpha's Avatar
    Alpha is offline T S - Moderator
    CS Forums $upporter
    Join Date
    Feb 12, 2012
    Location
    Directly above the center of the earth.
    Posts
    2,780
    Thanks
    1,235
    Thanked 1,531 Times in 738 Posts
    Country: Christmas Island

    Default

    AFAIK, you are converting the radio to a type-accepted model, the European GM300/Maxtracs that had the narrow IF standard from the factory. and this was simply converting the US to the Euro model. Otherwise, it would be outright illegal to use such a radio on Part 90, and I'm not sure what kind of legal trouble they (M) could get into for telling their customers to do it. You may be correct, though and even changes from one type-accepted model to another may not be quite legal, either.

  5. #5
    Join Date
    Nov 29, 2012
    Location
    Great Black Swamp Midwest USA
    Posts
    287
    Thanks
    93
    Thanked 179 Times in 81 Posts
    Country: United States

    Default

    Nice write-up.
    Yes. Motorola is out of these.
    I checked a couple of the components also, and had no luck.


    Your search for item numbers beginning with HLN9576 returned 1 record(s).
    1.
    Item Number. HLN9576A * Item has been cancelled
    UHF 12.5K CONVERS/MOBILE
    Unit of Measure: 1 EA
    (Same result for VHF)


    Your search for item numbers beginning with 91-80022M03 returned 0 record(s).
    Please refine your search criteria and try again.

    Your search for item numbers beginning with 91-80097D04 returned 0 record(s).
    Please refine your search criteria and try again.
    Common sense is Uncommon.
    You can't fix stupid, but eventually it takes care of itself.

  6. #6
    Join Date
    May 09, 2012
    Posts
    162
    Thanks
    14
    Thanked 28 Times in 19 Posts

    Default

    The narrow band GM300 could be purchased in the US. I don't have access to one to see if the type accepted number was the same as the wide band.

    Joe

  7. #7
    Alpha's Avatar
    Alpha is offline T S - Moderator
    CS Forums $upporter
    Join Date
    Feb 12, 2012
    Location
    Directly above the center of the earth.
    Posts
    2,780
    Thanks
    1,235
    Thanked 1,531 Times in 738 Posts
    Country: Christmas Island

    Default

    Thanks for searching, Bobby, too bad but I assumed the worst there anyway... I know the 2nd IF filters can be obtained fairly easily, they are common 455 kHz filters, the 22M03 1st IF's might be a bit harder to find. They are made by both Toyo and NDK so they might be somewhat common too. Obviously Motorola themselves aren't going to be of any help here but thanks for checking.

    Joe - "Euro" was my own terminology, they in fact may have been US-sold models, I just got used to calling the narrowband GP300's and GM300's that, since narrowband was not prevalent on VHF or UHF in the U.S back then.

  8. #8
    tsunami_australia No Longer Registered

    Default

    Ah spewing I could have REALLY done with one of them narrow banding kits for an M120 I have here for a VHF base. Thanks for the write-up / info at least it is great to see people contributing like this.