Category: RF Pallet Design

  • LDMOS Amplifier Testing Setup

    LDMOS Amplifier Testing Setup

    Here’s the testing setup. The enclosure is “universal” and different pallets get dropped into it. In the pic you can see the exciter (Flex 6300), spectrum analyzer, power supply, dummy load, RF power meter, ammeter and oscilloscope. Hiding in the back is a inline RF sampler. The way I test and develop these amps is…

  • January 2019 LDMOS Amplifier

    January 2019 LDMOS Amplifier

    Here’s my latest dual 1K80H amplifier, mostly in pictures. Actually, this is not “my” design. I built this in an afternoon and it most resembles the Elecraft amplifier from the drains back (output section). The Elecraft output section design looked pretty elegant and simple. So I wanted to try and copy it and see how…

  • Single versus Dual Bias for LDMOS RF Amps

    Single versus Dual Bias for LDMOS RF Amps

    Last year I decided I would design and build a regulated temperature-compensated independently adjustable dual bias circuit for my 2x LDMOS amp. (what a mouthful) Why? Because I wanted to try an experiment which actually works in a class AB audio amp. This being the ability to adjust the bias to affect the mix and…

  • Biasing Schemes Revisited

    Biasing Schemes Revisited

    So I’ve gone around the block on this one. Tried a bunch of designs, studied a bunch of others and finally designed my own! The goals of the bias circuit include: #4 is the key. As a LDMOS heats up, Ids will rise and the gain changes, causing the LDMOS to drift into a less…

  • Transmission Line Transformer Testing

    Transmission Line Transformer Testing

    Jerry Sevick, W2FMI (SK) called this the “Soak Test.” He used it to run real power through the TLT network to check efficiency. It’s a pretty simple test whereby you simply run significant power through the TLTs and measure the temperature rise in the cores. If they get hot, they are not as efficient as…