ВЭФ 12 (Astrad VEF 12 Project) - including a transistor tutorial

[pwdrive]

I found the ARRL books ok, the cathode tap Hartley is easy enough to build, the cathode voltage is in phase with the grid voltage, that's what's needed for oscillation to occur, in phase feedback, no voltage gain with the cathode follower but there is current gain, the tapped tank coil is in effect an auto transformer.

Lawrence.

NM, since posting the above, I've been trying to find a more in depth explanation for the series fed Hartley oscillator, managed to find one today, scroll down to Fig. 213 for the schematic, a written explanation is given below that, it's for a transistor job but the analogy is basically the same for a valve job where the cathode is connected to a tap on the tank inductor:

http://www.rfcafe.com/references/electri...1-2-20.htm

Lawrence.