17-07-2020, 11:08 AM
Copy any of the 1950s Vidor, but use 2 x 1j24b as pentode mixer (osc to g2) and separate LO. 2x 1N60 as peak detector. You can try pairs of the resistor style coils as IF tuned with 220pF fixed and 47pF variable. About 560uH to 680uH depending on IF desired. I've not tried that trick for an oscillator. It depends if you want performance or minimalism. Use a tap on the PP3 stack for g2 supplies for IF, Osc and audio preamp. The osc doesn't need to be triodised, though you can try it.
If you have an old set of rectangular Philips valve AM/FM IFTs, they will work. You might need to use the 1j29b to replace a triodised DF97, I forget if the 1j24b works at VHF. Copy the Vidor Vanguard if you want AM/FM. No DK96, on AM it uses the VHF mixer/osc DF97 as the LO for MW & LW and then uses the g2 as the LO injection on a DF97 as the AM mixer (it's the FM 1st IF also). Even if only doing AM, it's a good design to copy. Use a pair of 1N60s as a peak detector and 1j24b preamp instead of a DAF96.
You can also use 2x Transistor IFTs coupled back to back (the base inputs connect via a capacitor), thus the collector load coils, which is the tuned bit really, are the anode load and grid feed. Cheap AM transistor radio kits on ebay. Some have 2 x audio transformers and some not. Obviously the transformers are no use for valves, but the ferrite rod, tuning cap and IFTs can be used. Though you need four IFTs for one IF amp.
If you have an old set of rectangular Philips valve AM/FM IFTs, they will work. You might need to use the 1j29b to replace a triodised DF97, I forget if the 1j24b works at VHF. Copy the Vidor Vanguard if you want AM/FM. No DK96, on AM it uses the VHF mixer/osc DF97 as the LO for MW & LW and then uses the g2 as the LO injection on a DF97 as the AM mixer (it's the FM 1st IF also). Even if only doing AM, it's a good design to copy. Use a pair of 1N60s as a peak detector and 1j24b preamp instead of a DAF96.
You can also use 2x Transistor IFTs coupled back to back (the base inputs connect via a capacitor), thus the collector load coils, which is the tuned bit really, are the anode load and grid feed. Cheap AM transistor radio kits on ebay. Some have 2 x audio transformers and some not. Obviously the transformers are no use for valves, but the ferrite rod, tuning cap and IFTs can be used. Though you need four IFTs for one IF amp.
