30-04-2023, 01:22 PM
(This post was last modified: 30-04-2023, 01:28 PM by Mike Watterson.)
Looks like a table model to me, and very nice too!
Even many US battery models had an RF stage. But also the heptode and octode mixer-oscillator common even in US mains sets radiates more on the aerial than the traditional Hexode-Triode Mixer-Oscillator used in UK and most of rest of Europe. It's also why mains valve sets have a triode RF amp on the VHF tuner (or Triodised pentode) because otherwise in-band radiation of the LO-Mixer is a problem, the gain isn't significant. Battery valve sets with VHF (DC90, then triodised DF97, see https://www.radiomuseum.org/tubes/tube_dc90.html ) had very complex carefully adjusted baluns to minimise re-radiation and thus often had two whips or a loop. More common on Continental Europe, no USA models and only two portable & 1 table model in UK.
So while the RF stage for MW (LW not used for regular USA stations, only beacons and aeronautical) is common on USA mains and battery sets it might be as much for reducing Heptode/Octode mixer radiation as extra gain. In UK and rest of Europe usually only sets with SW had an RF stage, but most used Hexode-Triode Mixer Osc.
A few mains and battery sets used a separate triode oscillator (and if a heptode or octode used it was as a mixer only) but this was for stability and avoidance of a strong signal beside tuned weak signal FMing the oscillator rather than radiation concerns as such sets always had an RF stage.
See https://www.radiomuseum.org/r/hallicraft_s_72_s72.html which has 8 battery valves, RF stage, two IF amps, separate LO and BFO valves.
Typical Continental Europe battery valve AM/FM https://www.radiomuseum.org/r/philips_an...80_ab.html
The Ever Ready and Vidor AM/FM valve portable sets are untypical. The Ever Ready reflexes one RF valve as audio phase splitter for push pull and the Vidor uses FM 1st IF (DF97) as AM pentode mixer. The FM mixer/osc (DF97) is AM Local oscillator.
There may be a couple of European sets using dual conversion for FM. The DK96 is used on FM for 10.7 to 6.5MHz conversion, on many AM/FM battery sets the AM mixer/oscillator is off, though on some Philips models the DK96 grid is filtered and is the negative bias even on FM and Gram (so is kept on) for the push-pull output stage. It uses the DM70 as a triode phase splitter and power indicator rather than as tuning indication.
AFAIK all superhet AM/FM battery valve sets use the triodized DF97 (or early models the triode DC90) as additive mixer-osc with no RF stage, so can cause FM interference. Some mains sets use 2 x EF80, or ECF82 or ECC85, but all are actually an RF buffer and additive triode mixer-oscillator. Some late USA models used nuvistors for the VHF tuner, but they are just miniature valves.
[Edit there was one "novelty" single tube super-regen USA battery valve VHF model. No portables till transistors as FM was sold as HiFi, so only consoles from the start Band I before 1945, Band II from 1945. Germany had many AM channels taken by Allies, so FM started in 1949 and portable models almost as soon as DC90 was released. Ireland almost 1962 for FM Radio, but many received UK BBC FM from 1955)
Even many US battery models had an RF stage. But also the heptode and octode mixer-oscillator common even in US mains sets radiates more on the aerial than the traditional Hexode-Triode Mixer-Oscillator used in UK and most of rest of Europe. It's also why mains valve sets have a triode RF amp on the VHF tuner (or Triodised pentode) because otherwise in-band radiation of the LO-Mixer is a problem, the gain isn't significant. Battery valve sets with VHF (DC90, then triodised DF97, see https://www.radiomuseum.org/tubes/tube_dc90.html ) had very complex carefully adjusted baluns to minimise re-radiation and thus often had two whips or a loop. More common on Continental Europe, no USA models and only two portable & 1 table model in UK.
So while the RF stage for MW (LW not used for regular USA stations, only beacons and aeronautical) is common on USA mains and battery sets it might be as much for reducing Heptode/Octode mixer radiation as extra gain. In UK and rest of Europe usually only sets with SW had an RF stage, but most used Hexode-Triode Mixer Osc.
A few mains and battery sets used a separate triode oscillator (and if a heptode or octode used it was as a mixer only) but this was for stability and avoidance of a strong signal beside tuned weak signal FMing the oscillator rather than radiation concerns as such sets always had an RF stage.
See https://www.radiomuseum.org/r/hallicraft_s_72_s72.html which has 8 battery valves, RF stage, two IF amps, separate LO and BFO valves.
Typical Continental Europe battery valve AM/FM https://www.radiomuseum.org/r/philips_an...80_ab.html
The Ever Ready and Vidor AM/FM valve portable sets are untypical. The Ever Ready reflexes one RF valve as audio phase splitter for push pull and the Vidor uses FM 1st IF (DF97) as AM pentode mixer. The FM mixer/osc (DF97) is AM Local oscillator.
There may be a couple of European sets using dual conversion for FM. The DK96 is used on FM for 10.7 to 6.5MHz conversion, on many AM/FM battery sets the AM mixer/oscillator is off, though on some Philips models the DK96 grid is filtered and is the negative bias even on FM and Gram (so is kept on) for the push-pull output stage. It uses the DM70 as a triode phase splitter and power indicator rather than as tuning indication.
AFAIK all superhet AM/FM battery valve sets use the triodized DF97 (or early models the triode DC90) as additive mixer-osc with no RF stage, so can cause FM interference. Some mains sets use 2 x EF80, or ECF82 or ECC85, but all are actually an RF buffer and additive triode mixer-oscillator. Some late USA models used nuvistors for the VHF tuner, but they are just miniature valves.
[Edit there was one "novelty" single tube super-regen USA battery valve VHF model. No portables till transistors as FM was sold as HiFi, so only consoles from the start Band I before 1945, Band II from 1945. Germany had many AM channels taken by Allies, so FM started in 1949 and portable models almost as soon as DC90 was released. Ireland almost 1962 for FM Radio, but many received UK BBC FM from 1955)
