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kalee20 · 19th Mar 2008, 8:25 pm

Hi Dom,

Gosh, it's growing isn't it??!

As the standing current varies, a resistor / capacitor combination is no good as the resistor value will need to be altered too often while you adjust other things.

A potential divider will probably waste too much power.

The Zener diode idea is best (apart from more PN junctions infecting the circuit). I'd rate the zeners for peak current, then you know that whatever you do during development, you won't fry them. As an alternative to having the diode raise the cathode/grid-leak voltage of the final RF amplifier, you could instead connect the diode between the cathode of the cathode follower and the RF choke, thus dropping 20V from the modulator output.

19th Mar 2008, 8:25 pm	#83
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,077	Re: AM Micro Transmitter Hi Dom, Gosh, it's growing isn't it??! As the standing current varies, a resistor / capacitor combination is no good as the resistor value will need to be altered too often while you adjust other things. A potential divider will probably waste too much power. The Zener diode idea is best (apart from more PN junctions infecting the circuit). I'd rate the zeners for peak current, then you know that whatever you do during development, you won't fry them. As an alternative to having the diode raise the cathode/grid-leak voltage of the final RF amplifier, you could instead connect the diode between the cathode of the cathode follower and the RF choke, thus dropping 20V from the modulator output.