01-10-2016, 08:51 AM
Look at the Vidor Vanguard FM/AM set as it's all DF97s apart from the audio. But use the Philips LD480 and similar for the VHF front end. The Vanguard uses the VHF Mixer/Osc as AM Local Osc, and then the 1st DF97 10.7MHz IF amp becomes AM RF in/Mixer (No DK96).
You need two rod tubes to simulate a DK91/DK92/DK96. One is triodised as Osc. It feeds g2 as mixer LO in on a second rod pentode. Iv'e wired this on a B7G base and verified it works in a DK96 radio set.
The CR2025 can't safely supply much current, with no audio stages (only adds two valves, use 3 x 1N60 for FM and AM detectors) you'd need two stacks paralleled. Using 20 coins per stack. Less will be very poor. Four stacks in parallel will add enough for output stage and then it fits in a B101 box. Though a custom battery pack with a 50V approx tap to feed all the g2 connections is more stable and less waste than other methods.
If you want "hybrid" and small, then use only 1j42a as they can run from the same 9V (say 6 x AAA) as the Audio amp. Though I don't know how well the 1j42a work at VHF.
The 1j24b and 1j29b will work as a VHF Self Osc Mixer, identical to DC90 in the early Philips sets. I've verifiied that the DF97 is always wired as a triode for VHF mixer/osc and they are actually interchangeable without noticeable shift in VHF tuning.
You need a balanced RF coupling (see Philips circuits) on input, otherwise your VHF aerial will massively radiate LO, as unlike mains sets there is never a buffer amp in front of mixer Osc on VHF. USA sets commonly added 1T4 /DF91 or similar in front of DK9x to stop LO radiation even on MW only models. UK sets only bothered on high end models with Shortwave.
There was only one USA portable VHF tube set, a poor one tube regenerative set, though FM was on Band 1 in 1930s to 1945 and Band II from 1945-1946, because it was sold as HiFi and only on mains console / table / radiograms.
Netherlands, Denmark, Germany and Austria had the best ranges of pre 1960s tube VHF/AM portable radios.
I'd not try copying the Sky Emperor. That reflexes the 1st FM IF as audio phase splitter for push pull.
A good few Schuab Lorentz are dual conversion on VHF. Most VHF sets switch off the DK96 (though the Philips Colette* runs it on Gram and VHF to provide negative bias for output push pull!). The Schuab 1st IF is 10.7MHz. Then the DK96 adds gain by conversion to 6.5MHz for the rest of the IF amps (shared with AM IFTs).
(*Curiously the grid of LO goes up to 9V negative, so no diode needed, just a low pass filter of 2 x 1M or 2M (I forget which) decoupled twice to grids of the output DL96 push pull. The Colette uses the DM70 purely as power indicator and -1 gain phase splitter even though it *DOES* have a second DAF96. The second DAF96 is purely an active tone control! Swapping a couple of wires makes the DM70 /DM71 display AGC level and used the tone control amp as phase splitter. I can't figure why Philips did that. Mod reversible in less than 10 minutes!)
You need two rod tubes to simulate a DK91/DK92/DK96. One is triodised as Osc. It feeds g2 as mixer LO in on a second rod pentode. Iv'e wired this on a B7G base and verified it works in a DK96 radio set.
The CR2025 can't safely supply much current, with no audio stages (only adds two valves, use 3 x 1N60 for FM and AM detectors) you'd need two stacks paralleled. Using 20 coins per stack. Less will be very poor. Four stacks in parallel will add enough for output stage and then it fits in a B101 box. Though a custom battery pack with a 50V approx tap to feed all the g2 connections is more stable and less waste than other methods.
If you want "hybrid" and small, then use only 1j42a as they can run from the same 9V (say 6 x AAA) as the Audio amp. Though I don't know how well the 1j42a work at VHF.
The 1j24b and 1j29b will work as a VHF Self Osc Mixer, identical to DC90 in the early Philips sets. I've verifiied that the DF97 is always wired as a triode for VHF mixer/osc and they are actually interchangeable without noticeable shift in VHF tuning.
You need a balanced RF coupling (see Philips circuits) on input, otherwise your VHF aerial will massively radiate LO, as unlike mains sets there is never a buffer amp in front of mixer Osc on VHF. USA sets commonly added 1T4 /DF91 or similar in front of DK9x to stop LO radiation even on MW only models. UK sets only bothered on high end models with Shortwave.
There was only one USA portable VHF tube set, a poor one tube regenerative set, though FM was on Band 1 in 1930s to 1945 and Band II from 1945-1946, because it was sold as HiFi and only on mains console / table / radiograms.
Netherlands, Denmark, Germany and Austria had the best ranges of pre 1960s tube VHF/AM portable radios.
I'd not try copying the Sky Emperor. That reflexes the 1st FM IF as audio phase splitter for push pull.
A good few Schuab Lorentz are dual conversion on VHF. Most VHF sets switch off the DK96 (though the Philips Colette* runs it on Gram and VHF to provide negative bias for output push pull!). The Schuab 1st IF is 10.7MHz. Then the DK96 adds gain by conversion to 6.5MHz for the rest of the IF amps (shared with AM IFTs).
(*Curiously the grid of LO goes up to 9V negative, so no diode needed, just a low pass filter of 2 x 1M or 2M (I forget which) decoupled twice to grids of the output DL96 push pull. The Colette uses the DM70 purely as power indicator and -1 gain phase splitter even though it *DOES* have a second DAF96. The second DAF96 is purely an active tone control! Swapping a couple of wires makes the DM70 /DM71 display AGC level and used the tone control amp as phase splitter. I can't figure why Philips did that. Mod reversible in less than 10 minutes!)
