1922 one tube home brew radio - Page 1
Forum section: electronics / general

author: Tom45
author_rank: Frequent Contributor
timestamp: February 10, 2017, 02:52:49 am
content: This one tube radio in the local county museum was built in 1922. It is a single triode regen receiver.The controls as best I can figure out are:Large dial in upper left is connected to the variable capacitor.Two dials in lower left move coil positions to vary the inductance of the tuning coil.Small knob top center is a small variable capacitor connected to the large variable capacitorThe two controls at the bottom right are for filament and plate voltage. I haven't traced it yet to see which is which.The circular screen is apparently to watch the tube's filament glow when adjusting the filament voltage.The tube is a UX200 triode.The middle coil is fixed. The two outer coils each have a knob to adjust the distance between them and the center coil.The binding posts in back are for filament and plate batteries. Headphones probably connect to the front panel posts, but with 4 connections there is more to it than that.Anyone have information on this? I don't know if this was a kit or it was put together from parts he bought separately. The coils and gear mechanism to move them wasn't something he would have found in his local hardware store.With controls for filament voltage, plate voltage, 2 tuning capacitors, and two inductors, it must have been a real art to adjust it for good reception.

author: John_ITIC
author_rank: Frequent Contributor
timestamp: February 10, 2017, 03:26:15 am
content: No further information from me but I'm amazed how far humanity has gone in less than 100 years. I wish I could imagine what technology will look like 2117. Even today it is magic...

author: Ian.M
author_rank: Super Contributor
timestamp: February 10, 2017, 06:10:59 am
content: The far end pair of binding posts only connect to the far end adjustable coil, so I would expect them to be the antennae and earth connections, and the knob on the bottom left of the front panel to be the antennae coupling control.I would expect the next knob along to be the regeneration control - its got to have one somewhere and none of the other controls are suitable.Its likely that the HT supply was on the front panel binding posts, which seem to be involved with what initially appears to be a wiper switch and the headphones connected to the wander jacks. The wiper 'switch' only has two end connections to its studs so must actually be a stepped potentiometer. That would leave the remaining pair of rear binding posts for the filament accumulator and the wirewound rheostat to control the filament current.The UX200 is a 'soft' triode with a trace gas fill, and 'soft' valves didn't have a good reputation for long-term reliability, the grid leak resistor next to the valve socket (under the grid coupling condenser) has probably gone bad and all bolted connections have probably oxidised enough to give trouble, so the chances of restoring it to working order without compromising its historical authenticity would be fairly low.

author: calexanian
author_rank: Super Contributor
timestamp: February 10, 2017, 09:48:27 pm
content: Looks pretty nice. I bet it would still work. Old gas tubes like that have a unique noise. Its kind of an irregular thumping or even gurgling (For lack of a better term) as the conditions vary in the tube due to the evolution of gas from surfaces that condensed while the tube was cold but get liberated by heat as it is used. Once barium based getters were economical gas tubes were quickly made obsolete.