11-12-2016, 06:47 PM
(11-12-2016, 11:51 AM)Mark Hennessy Wrote:(10-12-2016, 10:37 PM)Murphyv310 Wrote: Hi Michael.
I'm not so sure if you're comments really are helping in this project, are you implying this wont work?? Looking at the spec there is no reason to say it wont plus I have proof it does and that my friend is the ultimate end I've done.
I'm somewhat disappointed at your comments after proving this very simple TX works.
Come on Trev - no need to be defensive. I've read Michael's posts carefully - they contain interesting theory about the rod pentodes, but no criticism of your project.
Like many, I've enjoyed reading this and seeing/hearing the results. Ignoring the preamp, it's amazing what can be done with just one active device! Keep up the good work
Mark
@Trevor No criticism intended at all.
I'm only explaining why the dual grid is NOTHING like a differential amplifier (almost the opposite!) and NOTHING like how a dual gate FET works. Unlike every other device, the g1a and g1b is a split connection to the normal TWO grid plates in any rod pentode.
I'm repeating the theory from the Russian data, translated Russian articles (by Demetri) and added to by Joe Sousa's tests and disassembly. Joe is extremely expert.
In practice almost any circuit works (even unlikely ones) as oscillator, amp or mixer with rod pentodes. You can even inject modulation at g3 or anode, especially with the regular types using only 15V to 22V HT.
However understanding the theory allows optimisation of the circuits and good & reliable performance.
Top view of the two beams. Applies to 1j17b, 1j18b, 1j24b, 1j37b and 1j42. The 1j29b and 1p22b and 1p24b have a second filament and parallel pair of beams.
On the 1j17b, 1j18b, 1j24b, 1j29b, 1p22b and 1p24b the g1 plates are all internally connected.
On the 1j42a and 1j37b the two g1 plates either side of the filament are separate, g1a and g1b. So if g1a is tied to g1b the 1j37b is similar to a 1j18b and the 1j42a is similar to a 1j24b, but lower HT due to closer spacing of g2, g3 and anode. There is another unusual feature of the 1j42a as unlike 1j37 it's more customised (the 1j37b is a simplified 1j18b and has even less screening!)
General construction:
1j37b (high power version of 1j42a) top view
Push Pull TX (1p24b), 220mA @ 2.4V, 440mA @ 1.2V
Russian circuit, portable military
Triodised this can do 1.6kW peak for radar in a proximity detector of a shell etc, (shorter life!)
More shortly...
