300W 432 Mhz linear amp that won't break the bank

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by VE4CY, Apr 12, 2016.

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  1. VE4CY

    VE4CY Ham Member QRZ Page

    So I thought I'd get on 432 CW/SSB this summer. I've got a long boom 19 element beam fed with Heliax.

    I'm just using a Kenwood TS-2000. It gives me 35 Watts out. I'd like to raise that by about 10 dB with a solid state amp.

    I looked around and the first thing I notice is that you can't get these at the regular outlets (Universal, HRO etc). Many come from Europe (Gemini, Beko etc) and are up in the $1500 - $2000 range.

    I've done a lot of searching, but can't find anything reasonably priced. Is there as secret place VHF/UHF guys get their gear? :)
  2. AH6LE

    AH6LE Ham Member QRZ Page

    WA7PRC likes this.
  3. KM3F

    KM3F Ham Member QRZ Page

    This is the situation with amplifiers, they cost money in the upper frequency ranges.
    Try to find anything for 222 band under $800.
    They are to be built on special order.
    I lucked out on cheap commercial amplifiers simply because no one wants them as they need retrofitting for Ham use, and can even be combined for 300 watts if one wants to go that far.
    For 432, you have an option of using a pair of 4cx250/300 or 350 ceramic tubes to get the power you want but you need to build a power supply to run it.
    The bottom line is, effort has to be made to build the equipment, buy it, or your out of luck.
    The older VHF hand books show these amplifier circuits and power supplies.
    Good luck..
  4. VE4CY

    VE4CY Ham Member QRZ Page

    OK, thanks guys...

    I am handy and have built my own stuff in the past. I balk a bit at VHF/UHF stuff because there's more to it than connecting wires. Everything that isn't positioned correctly has the potential of being an unwanted capacitor or inductor.

    I haven't built anything in quite a while. Perhaps I'll take a crack at it :) Thanks for the links.
  5. AH6LE

    AH6LE Ham Member QRZ Page

  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    An 8874 can run about that much power with the drive you have available and might be cheaper to build if you can find the tube.

    Here's one design: http://oz2oe.dk/radio/8874pa/8874.html

    A 4CX250B which costs less can also be used with a more complex power supply, correct socket and quite a lot less drive (about 5W) following basically the same design.
  7. K6CLS

    K6CLS Ham Member QRZ Page

    if you get lucky you might find an old TE Systems amp ($350?); or a Henry 2004 ($1500?), or even better a K1FO ($4000?). However time is money, why not go for a Beko?
  8. WA9WVX

    WA9WVX Ham Member QRZ Page

    Here's a tube RF amplifier that can be modified to do 400 Watts PEP Output, a respectable signal on 70 cm for CW & SSB. These modified RF amplifiers are very common on 432 MHz.

    Fair Radio Sales has been around since 1947 after WW II.

    AM-6155 RF Amplifier https://www.fairradio.com/catalog.php?mode=viewitem&item=2208

    You'll also need a Bias Supply BS-6155


    And a schematic for the Bias Supply

    SCH-BS-6155 - Schematic for Bias Supply

    You can substitute a 4CX400A when the original tube gets weak.

    Here's a modification for this RF amplifier http://ve2zaz.net/AM6155/AM6155.htm

    Here's another modification for the RF amplifier http://k4hv.flwss.net/AM-6155-432MHz.html

    Here's another modification for the RF amplifier http://www.packratvhf.com/Article_1/Article1.htm

    Here's another modification for the RF amplifier


    One of the four modifications or all four should provide you with enough information how this should be accomplished.

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