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Thread: Astro FrankenSpectra...Band Change?

  1. #1
    PSYKO_Inc No Longer Registered

    Default Astro FrankenSpectra...Band Change?

    [Edited by Mars: Please use paragraphs, instead of a giant block of text. Thanks!]

    I recently happened upon a Q-split Astro Spectra RF deck from a consolette. Haven't read the radio yet but I'm told it most likely is flashed for P25 operation.

    Also did some digging in the parts bin and found a clean W7 head, remote housing, and remote cable. As a ham, Q-split is worthless to me, and there's really not much UHF ham activity around here anyway.

    About a year ago I picked up a high power VHF analog Spectra RF deck on Ebay for about $30, which arrived with bad caps and missing its MLM. A generous Batlabs user sent me a couple MLMs to play with, but making it work would would require a certain software that shall not be named that I don't have at the moment, and the project managed to turn into one of those "round tuits" that I never found the time for.

    My question is, would it be possible to use the Astro's command board and VOCON in the VHF analog Spectra along with the appropriate S-Record to build a functional equivalent of a high power VHF Astro Spectra? I've read there are some differences in the RF boards between wideband and narrowband Astro Spectras, but is there any difference between the wideband analog and Astro boards?

    Alternately, is there any way to modify a UHF board to change it to VHF? The Astro RF board is narrowband, which would be nice to have the option, but wideband-only wouldn't be a show stopper if the boards would swap right over.

    This is my first venture in playing with the Astro Spectra, so I'm sure I'm probably missing something here. If anyone has done anything like this, your expertise would be much appreciated.


  2. #2
    PSYKO_Inc No Longer Registered

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    A couple more details in case anyone is interested:

    - The donor radio is an L04QKH9PW9AN-UCM with a 1 meg VOCON.
    - The RF board on the donor radio is NOT narrowband like I had previously thought, board number is HRN6020G (I think, the ink had bled on the label so the last digit could also be a C or Q.)
    - From my research, it does appear that RF boards are band-specific, so the UHF RF board is no good to me at this point.
    - I read the radio and got flashcode 140004-000000-0, which gives me IMBE, multikey encryption, and Smartnet.
    - The VHF radio I'm looking to convert is a T83GXA7HA7AK.
    - Recipient radio has RF board number HRN6004C. Still don't know if there's any functional difference between analog and Astro RF boards.
    - Still searching for an appropriate S-record.

    At this point, I'm debating on whether to just try to cobble it together with the VHF analog RF board and see what happens, search for an Astro VHF RF board, or pick up a cheap R3 UHF Spectra and GMRS like a boss...

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    Yes it can be done, you can take the entire logic board, Vocon and RF board from the "Q" split radio and put it in the VHF chassis, but there have been some comments that you have to change some resistors on the RF board to get the P-25 to work correctly. I didn't have that problem, and you will also have to get an appropriate "S" record for the type of head and band split you have and dump it in. Information abounds here on how to do it, I have personally done 4 800mhz to UHF conversions with no problems.

  4. #4
    PSYKO_Inc No Longer Registered

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    Thanks for the info. Can you give me any more info on what resistors need to be changed? There's only one VHF P25 amateur repeater in the area that I know of, and it's 40 miles away so I don't know if I could get in or not, but it's definitely something I'd like to try.

    On S-records, does the logic board "know" whether it's in a high-power or low-power chassis? Or does it send low-level RF into the PA, and whatever comes out the other end depends on the PA itself? I've got a 50W VHF W7 Astro Spectra at work that I could copy the S-rec from but wanted to make sure I'm not going to screw something up by putting it in a high-power chassis. Obviously it will need a full alignment afterwards since the tuning data will be off but that shouldn't be a problem since I have a full test bench at my disposal.

  5. #5
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    The RF board may need more changes than just a resistor or two. It might be easier to try and find a rev "C" or later VHF RF board by itself than to try and convert one. There are several threads on here already about this, use the Google "site:p25.ca" option and that will search the site here better than the on-site search function.

    You are correct about the PA it doesn't know - you just need to align the PA to the proper power level appropriate for the type it is, 100W or 40W, etc.