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Thread: Spectra analogue mode power vs frequency problems

  1. #1
    spectra No Longer Registered

    Default Spectra analogue mode power vs frequency problems

    I have issues with an earlier conventional spectra high power 450-482mhz radio where as soon as i enter a frequency above 470mhz it blocks out the high power output selection.
    Any suggestions or ideas as to how i can rectify the problem would be greatly appreciated thanks.
    Even if i could use a switch on the p.a side somehow.


  2. #2
    Will No Longer Registered

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    Maybe a bad codeplug that is causing this. I would like to look at your codeplug.

  3. #3
    spectra No Longer Registered

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    How can i go about sending it to you . .

  4. #4
    Will No Longer Registered

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    With your file manager, look in the Spectra/archive folder, SPARCHIVE, for a file like A617HVE0.185 (your radios serial number) AND the SPECTRAM.DBF the Spectra DB file. Email these two files and I can look at the codeplug.

    There may also be a B file with your radios serial number, that would be the 'backup' file.

  5. #5
    spectra No Longer Registered

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    I have also been working on the p.a trying to figure out a way to have a high low power select.
    I have checked voltages keyed and unkeyed and also adjusted the power in the tuning software and found the control voltage and tied it to a keyed voltage for testing and it works but i need more of an understanding on how the circuit works that supplies the power output control voltage .
    I will upload pics with voltages etc .
    I was thinking of connecting it to the horn lights circuit maybe.

  6. #6
    spectra No Longer Registered

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    spectra 003.jpgspectra 005.jpgThe pin marked in red seems to be the control of the output power when joined to the pin in pink wich is 9.4 volt it gives me high power when normal keyed power for the pin at 50 watts is about 5.5 volts

  7. #7
    Will No Longer Registered

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    Spectra,

    I looked at your radio's codeplug. Any MODE, channel, is defaulted to LOW on both TX and Talkaround above 470.0125 and it seems to be something in the RSS. I think because the T Band has TX power restrictions. Works below 470, allows either setting. The Mid Pwr (T44KXA) radios do not have this restriction

    The power control is set by a D-A converter that feeds a OP Amp and driver on the Command board that controls the low level stage in the PA.
    Last edited by Will; Sep 30, 2013 at 12:44 AM.

  8. #8
    Join Date
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    T Band is restricted for ERP, depending on which TV channel you are using. I remember from Micors that that had values like 54 watts output listed near the power control. I wasnt aware that they coded that info into the Spectras

  9. #9
    spectra No Longer Registered

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    Is their a way to find it in the spectra rss and change it.

  10. #10
    vk2hwy No Longer Registered

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    With CPS you can hex edit to change the band limits, I wonder if you could do similar with the RSS in relation to the power restrictions?

  11. #11
    vk2hwy No Longer Registered

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    Quote Originally Posted by spectra View Post
    I have issues with an earlier conventional spectra high power 450-482mhz radio where as soon as i enter a frequency above 470mhz it blocks out the high power output selection.
    Any suggestions or ideas as to how i can rectify the problem would be greatly appreciated thanks.
    Even if i could use a switch on the p.a side somehow.
    Perhaps changing the 470 value in the Spectra1.exe, Spectra2.exe and Service.ovl folders to 480 may fix your problem?

    Anyone else have thoughts on that mod?

  12. #12
    spectra No Longer Registered

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    I had looked into that a while ago but for me understanding hex and converting it etc it was like trying to learn some alien language.
    There was a bit of info about for editing band limits but as for the power limit i couldn't find anything.

  13. #13
    vk2hwy No Longer Registered

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    Quote Originally Posted by spectra View Post
    I had looked into that a while ago but for me understanding hex and converting it etc it was like trying to learn some alien language.
    There was a bit of info about for editing band limits but as for the power limit i couldn't find anything.
    I've hex'd & check summed the three folders I mentioned in my post above. In the next day or so, when I have time I will test and let you know how it goes.

  14. #14
    Will No Longer Registered

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    One way to get around the OP original problem, power output above 470 mHZ, would be the align the Low Power to what you need and are allowed on the T Band.

    High Power UHF Spectra radios do not like anything less than 60 watts on low power. Anything less seriously overheats the Power Amplifier. The PA is a class C circuit and the efficiency goes way down below 60 watts.

  15. #15
    spectra No Longer Registered

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    That would be interesting.
    I was thinking about making two backup files of the codeplug one with a high power and one with a low on one channel then comparing the saved data to see what actually changes .

  16. #16
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    "I was thinking about making two backup files of the codeplug one with a high power and one with a low on one channel then comparing the saved data to see what actually changes.

    That's a neat idea all T band freqs are power limited in mobiles to 75 watts max, but you could have up to a 5db gain antenna. That's what I remember on the Micor mobiles I used to put in back in the 70's. Kinda bass ackwards considering you could have up to 1.1kw ERP (over 720w ERP on 450)on base repeater operations.
    NYC EMS ran 275w Micor repeaters with 10db Super Stationmaster antenna's, the mobiles were 75w with 5db broom stick antenna's. That was at least until they all got bashed by trees,parking garages,and everything else.They were then replaced with unity whips.

  17. #17
    vk2hwy No Longer Registered

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    This may be another way around the problem:

    https://www.p25.ca/threads/4574-Spec...7687#post37687