08-08-2023, 08:06 PM
Stuff can look totally original and not be!
I've used Russian 1j24b rod pentodes on home made adaptors to replace all the B7G battery valves on parallel LT. An added 1N60 as detector and 1/2 filament 1j29b for DL96 and both for DL94.
Two 1j24b for DK types, one as pentode mixer (signal g1, LO g2) and one as triodised osc with anode driving pentode g2, direct coupled.
The DF9x replacement needed a pull down resistor to set g2 (g2 volts sets gain).
Disadvantage is there is no RF or IF agc because of sharp cutoff.
I probably have stock of all B7G battery types now except IL6. A DK92 has similar performance, and works in socket, but HF alignment madly bad. So I started to do a version of the dual 1j24b mixer/osc with ballast resistors for 50ma Series and trimmer caps as the 1j24b is much lower capacitance on anode and all grids. The MW/LW replacement is no issue as you can tweak the IFs, but mimicking the anode Capacitance avoids that.
The Sky Queen (and all the similar chassis) work well. I think good Q IFTs and well matched not too small loop aerial.
I've used Russian 1j24b rod pentodes on home made adaptors to replace all the B7G battery valves on parallel LT. An added 1N60 as detector and 1/2 filament 1j29b for DL96 and both for DL94.
Two 1j24b for DK types, one as pentode mixer (signal g1, LO g2) and one as triodised osc with anode driving pentode g2, direct coupled.
The DF9x replacement needed a pull down resistor to set g2 (g2 volts sets gain).
Disadvantage is there is no RF or IF agc because of sharp cutoff.
I probably have stock of all B7G battery types now except IL6. A DK92 has similar performance, and works in socket, but HF alignment madly bad. So I started to do a version of the dual 1j24b mixer/osc with ballast resistors for 50ma Series and trimmer caps as the 1j24b is much lower capacitance on anode and all grids. The MW/LW replacement is no issue as you can tweak the IFs, but mimicking the anode Capacitance avoids that.
The Sky Queen (and all the similar chassis) work well. I think good Q IFTs and well matched not too small loop aerial.
