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Thread: VHF Power Amp question

  1. #1
    standardmissile No Longer Registered

    Default VHF Power Amp question

    After chatting with Alpha via PM I figure it might be a good idea to ask this publicly.

    The PA on the Astro Spectra is about 50% efficent. Is there any way to optimize performance from only 150MHz down on a K band unit? For work/play I only frequently Tx in the 136-155 and would greatly appreciate less drain on my PSU or vehicle alternator. If it can be tuned/modded to give me another 5-10% current drain, with a DIY requirement that would make it worthwhile for me.

    Also, stay tuned for some pics of a more unusual sensitivity adjustment I'm in the process of cooking up for the Spectra line....

  2. #2
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    In case this preamp info is of interest:

  3. #3
    standardmissile No Longer Registered


    Thanks, I had something similar in a printout from a friend, but that makes it a lot easier to do.

    However I am modding a different subcomponent ATM. The coax on the inside of the unit that takes the signal from the RF board into the PA and from the PA to the antenna jack are RG-58U sprigs. I noticed that on my units the shielding/diaelectric is cut away from a significant amount of the copper wire (about 5mm on the PE, and another 7mm of the shield) leaving it bare. I'm removing that cabling and instead replacing them with RG-8 (solid CU, quad shield) pieces with the metal shielding covered in a dab of liquid electrical tape, so that both can sit snug up against the PC board they pass through. This in theory should increase the sensitivity by decreasing the leak on the signal path, decrease signal attenuation (however little it is) and increase the shielding on the existing design, thereby decreasing any noise on the circuit.