Pentodes as grounded-grid RF amps?

[MichaelR]

Originally Posted by kalee20

For true comparison, you'd need to do the calculations, and at this point I'd have to say I've never done any RF noise calculations (or made a 100MHz RF amplifier). But, this is my gut feeling - best practice would be use a cascode double-triode amplifier, a triode mixer, and a separate triode oscillator. Four triodes!

More valves more cost.. however I must say I like your design ideas

mike

[Neil Breward]

Originally Posted by ppppenguin

I I can't immediately find any references to support my claim but this website is interesting:

http://wb0nni.dakotamade.com/ggbasic.html

Jeff - sorry, didn't notice this earlier. Interesting web site, but anyone who starts off saying:-

" Input signal is 180 degrees out of phase with the output signal, virtually eliminating the potential for self-oscillation and tube take-off."

:- when discussing grounded-grid circuits, is really scoring a classic own goal!

Cheers,
Neil

[ppppenguin]

Originally Posted by Neil Breward

Input signal is 180 degrees out of phase with the output signal, virtually eliminating the potential for self-oscillation and tube take-off."

You're right. I didn't spot that. It's just possible that it's a poor translation for the author's first language is clearly not English.

[MichaelR]

Positive feedback leads to oscillation not negative...Yes?