Temporary 50-100 watt linear

Discussion in 'Homebrew and Kit Projects' started by W4KJG, Oct 17, 2021.

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  1. W4KJG

    W4KJG Subscriber QRZ Page

    I have an old thread about my Ten Tec 540. I have again done something bad to the PA of this Ten Tec 540.

    I have a fair amount of experience designing and repairing modules like this. I spent several hours trying to figure out what failed this time. I don't want to put any more time into trying to repair it until the snow starts to fly.

    For the interim, I want to replace this amplifier with an external PCB or module that provides about 50-100 watts over 2-30 MHz, running class AB1, if I can find such a thing for less than about $100.

    The original module has RF connectors at the input and output, and +12 to +15 VDC power input. The driver signals pass through good bandpass filters for each band. The transmitter provides an adjustable drive level up to a minimum of about 3 watts. The amplifier output feeds band selected low pass filtering for each band to the antenna connector.

    All I really need is a PCB and parts, assembled or not. I want it to provide between 50-100 watts output when supplied with about 13.5 VDC. It would be nice if the PCB/module was 5-1/2 x 3-1/4 inches or smaller.

    Several years ago I built a home brew 50 watt unit that meets these specifications, but I have it installed in another transceiver. It is built on perfboard, with the driver transistors and final amplifier transistors mounted to a heatsink. I just don't really want to pull it from that transceiver for this transceiver, and I don't really have the time to spend ordering the cores, winding the transformers, coils, drilling a heatsink, etc.

    All suggestions welcomed.

  2. WA4SIX

    WA4SIX Ham Member QRZ Page

    Pillage an old Kenwood TS-440 ish rig. Simple to use & control.
    I use the amp & filter board with an SDR & control them with an arduino. Been working for almost 3 years now.
    You can often pick up an older rig like this that needs repair for some other reason, cheap.

  3. N2CI

    N2CI Ham Member QRZ Page

    If you can live with 20 watts, I have an extra circuit board, and could put together a package of parts for you. It would require winding transformers, and drilling / tapping the heat sink. It would also require soldering some SMD components. This is based on two RD16hhf1 MOS FETs. You would also need adequate test equipment to verify it is working properly prior to putting it into service.
  4. K5DH

    K5DH Ham Member QRZ Page


    I've seen some inexpensive HF amplifier kits offered for sale on eBay. Most have no output filtering, but, as you state, the 540's bandpass filter board is already in the circuit. Might be worth looking into.

    Another possibility would be a CB-type solid state amp. They were made to operate at the 3-5 Watt input level. You may have to mess with the bias to get it to run true AB1.

    You might be able to snag another 540 to use as a parts source. I've bought restorable 540s for as little as $25 at hamfests and under $100 shipped on the internet. Keep your eyes peeled.
  5. W4KJG

    W4KJG Subscriber QRZ Page

    Thanks to all. Someone has offered a TS-440 amplifier to me.

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