Please read the description first, also for safety issues when you want to make such an old 1 tube radio of the 1920’s.

I thumb through an old Dutch radio Book of 1926 (first issued) or 1928 (second time issued). Showing some essentials about the circuits and the materials (tuning capacitors, etc.) that were used in those days.

Book Title: "Het Radioboek voor den Handel, Amateur en Luisteraar", door ing. J. Schiere, issued by Karel C. Schoemeijer, Bussum, the Netherlands, 1928.

Title translation: in the video.

The linearity of the tuning capacitor for these old radios was a kind of issue in those days. In their first stages these radio’s (1920’s or so) were all “TRF” types.

The radio stations (with that TRF setup) did not show all the radio stations, properly dispersed on the scale, when tuning c.q. when the tuning capacitor was (not) made in a certain way. Has of course to do with the properties of the radio frequencies on LW and MW (also on SW). I mean with a “normal” tuning capacitor the radio stations popped up “very close together” when tuning, listening to MW or LW stations.

Could mean: Radio stations on Long Wave or Medium Wave could be heard together on frequency “X”. Thus: a selectivity ussue.

The radio technicians of those days (1926-1928) tried to cure that by giving the tuning capacitor plates a certain form. So that, when tuning was done, the capacitor values matched with a kind of frequency spread on the scale, showing the radio stations somewhat better apart. Please note: this was all during the “TRF Radio time”.

When the superheterodyne principle was found out (1920-1930) and used this problem was, in a certain way, “solved”. Though still present on Shortwave, with analog radio receivers.

Corrections and remarks to this video:

1) I often say “2024” where it now has to be “2025”.

2) Even now you can make such 1 tube (triode) radio for Long Wave and Medium Wave.

3) Thus between (say) 300 KC and 1.8 MC. Schematics (though not with a triode tube, only with transistors) are on my YT Channel. Schematics with a tube are in my (Dutch text!) book: “Retro Radio”, issued via Elektor in the Netherlands/the EU.

4) Supply the triode tube (like in 1926) with pure (battery-like) DC Voltages in those cases, both for the filament (can be between 1.2 Volt and 18 Volt, depends on the type of tube) and the High Voltage (between say 80 Volt and say 120 Volts DC). I have made such a TRF radio with a tube for MW and tested it. AC current to the filament of any tube (or to the High Anode Voltage) in this case will give an enormous (not curable) hum of 50 Hz or 60 Hz, that frequency depends on the AC mains from where you live on earth

5) When you want to use a headphone on the 1926 circuits showed in this video: it must be a 2000 Ohms type. A “modern” headphone (8-32 Ohm) does not work here. Putting such a 2000 Ohm headphone on your head, while there is 80 Volt or 120 Volt (that serves the triode tube) is dangerous. This is a disclaimer (!). Better option: use a 2000 Ohm resistor (1 Watt type) instead of that headphone and take the radio signal out via a 100 N (=0.1 uF) capacitor that can withstand 250 Volt. Supply that “output radio signal” (AM detection takes place in the triode tube) to a simple audio amplifier of any kind. For maximum safety: also use a 0,1 uF/250 Volt capacitor in the “earth/ground” line to the (-) minus of that all purpose audio amplifier. To make the radio signal audible.

Sorry for the misspelling of the name of engineer White.

Better idea: buy a transistor radio that can cover the LW or MW band.

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Next video (5 jan. 2025) is here (Old Radio book of 1937) [ Ссылка ]

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