Das Leithäuser Audion

I still had a few nice small battery tubes lying around, the 2SH27L, bought them at www.pollin.de for around 25cents/tube, bought 10 of them. I already made a cristal radio, but next level was a regenerative Leithäuser receiver. (back then also called a Reinartz receiver, but Prof Leithäuser had the patent for it some years earlier)

De radio is working perfect in it`s experimental setup without a coupled antenna, lots of stations coming in the evening,..but at daytime it is working better with a coupled antenna.

The regeneration is controlled by a  variable capacitor through a coil which is non adjustable towards the tuning coil. The anode of the first tube and surpressor grid (G3) are connected to earth because they are not in use, the radio is also working better when the grid (G2) is used as anode.
The way were the reg. capacitor is situated between coil and earth instead of anode and coil makes this setup heavily react on hand capacity, isolating the C with a plastic shaft will make things work better.

The radio also consumes little power, filament 2,2volts x 57mA = 125mW/tube. Anode-current for the complete radio is around 1mA.
 

The schematic drawing of this receiver has been changed over the year, so I had to draw a new complete one.
Capacitors were given in centimeters, so I had to recalculate these into picofarads. The coils were given in windings,..so I had to search the books of how these were made so I could write their values into microHenry`s. With the given L/C values the receiver should operate in the middlewave BC band. You can alter your coil values so they will match the capacitors you have on hand in your junkbox.

It is worth building this receiver,..it`s got a few nice honeycomb coils in it`s original design, I already got a few made and I already found some nice old "Pilot" variable air capacitors from this era.

Here the radio dials in design using autocad, printed onto transparancy and used to light brass sheet sprayed with photopaint for circuit boards.

Here the same design has been developed and is now being etched like I also do with printed circuit boards. The 0,75mm thick brass sheet has been etched for about 50 minutes. Then it has been cleaned, cut out, cleaned and sprayed black. When dry to "high" sides are being polished, so the paint is only in the "lower"parts of the dials. The again polished using copper polish and some turtlewax as used on cars.

Above you see the tube sockets for this receiver, completely homemade. I made the orginal on my lathe using wood, made a mould and created a new one using black colored resin. Contacts are made out of brass tubing, sheet and solid brass. Resin is supposed to isolate to around 10000volts, so good enough for a low voltage tube as a A411 or RE144.

And the dials and knobs put on the front side of the receiver. Three for the variable capacitors (2 tuning, 1 regeneration), and two for the heater current. And another 3 plates saying what the 3 knobs above are for. (in german, with Fraktur character type).
The book with the description and an old style 1925 headphone.
(click picture for big format old style picture)

PA2MRX©dec2010