Rick Karlquist N6RK wrote:

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

I played with that idea on the simulator. Didn't seem to have
a lot going for it.

I just did an FFT on a step-pulse on a diode-switched, binary weighted
LC ladder. Came out as I expected. Problem is the high-frequency
resonances exist on when the low frequency sections are not shorted.
Which will make transistor oscillator design interesting, if I don't use
a 50 ohm MMIC.

I've been following those nonlinear ceramics (ie BST) for years. They
don't seem very promising as a tuning diode replacement. The Q is too
low, the tuning range is too restricted, and there are temperature problems.

The latest Microwave News article showed the Q as being better than
varactor Q's, of under 10, IIRC.

--
Scott KB9ETU

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DIY Piezo-Gyro, PCB Drill Bot & More Soon!

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