Ham radio power adapter

Discussion in 'General Electronics Chat' started by techx, Feb 26, 2011.

  1. techx

    Thread Starter New Member

    Sep 21, 2009
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    I just bought a Motorola Mostar receiver, I have a couple issues with it and wanted to see if someone could provide some insight.
    • First is getting it powered. There is a hacked 2 power wire setup coming from it. I want to plug it into a cig lighter adapter and have found out the requirements to be : rated current draw for the radio is 7.4 amps at 30 watts.
    • Second is the model number states that it is a uhf receiver, the ebayer listed it as VHF 2m APRS, I have noted that there are mods to change the frequency band, but I have not found out any information to check this radio to determine if it has been modded or if the ebayer is due some back mojo for completely lying about an item. If I can identify the crystal or eeprom, whichever is the item that people replace to change frequencies in a radio like this, I'm sure someone might be able to let me know if this is UHF or VHF 2m.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. Adjuster

    Well-Known Member

    Dec 26, 2010
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    A receiver or a transceiver? 7.4A sounds like an awful lot of juice for a receiver, and doesn't seem to line up with 30 Watts, unless that's actually the TX RF output?
     
  4. techx

    Thread Starter New Member

    Sep 21, 2009
    14
    0
    Sorry, I didn't clarify, it is a transceiver. After opening the case I found the original SN for the frequency chip located on the chip and also on a label on the case that verifies it is an original UHF chipset. I do not know if these take a crystal to change frequencies or what I would need to do, but it looks like I'm already set back in the project.

    Andy from Brinkley sent me a message based on the model that it is 7.4amp 30watt rated power plug. At my calculation that is a 4v input to keep under the 30watt. That's just basic P=IV right? So if I wanted to use my cig lighter I would need to step down the voltage because a resistor is just not going to cut it unless it becomes a more complicated circuit right? I have not been able to find a stepdown of any kind that goes from 12 to 4v and allows over 1amp. Any insight?
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The 30Watts could be the RF power output. 30W output seems to be mentioned for some Motorola Mostar sets (See SgtWookie's 2nd link).

    You cannot therefore be sure of the DC input voltage being 4V.
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Unless this is a small hand-held unit 4V sounds completely wrong. Looking on the web, these things look like mobile rigs for vehicle use, so they might even be 12V.

    For goodness sake don't try that until you have found out the power requirements for certain, including which lead is positive!
     
  7. K7GUH

    Member

    Jan 28, 2011
    191
    23
    Forget the 4 volts. I can guarantee you with 99.998 percent certainty that it is designed to run on 12 volts d.c. or a multiple of 12 volts.

    Check the ampere rating on your cigarette lighter. They are not all heavy duty. However, I will speculate that the 7.4 amp load will not overtax it.

    If you are planning to buy a cigarette lighter plug, be sure it can handle the 7.4 amp load, and, if possible, get one with a self contained fuse.
     
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