Post by malewithatail on Apr 7, 2021 10:50:41 GMT 10
Above is a photo of the front panel of a homemade 3/4 valve regenerative radio receiver I made some time ago. It runs from 12 volts dc and has a 6CB6 valve as an untuned rf stage, a 6CB6 as the detector, and a 6GW8 triode/pentode in the audio stages. The valve filaments operate directly from 12 v dc, whilst the high tension is derived from a simple self oscillating dc to dc converter that also operates from the 12 v dc. Current consumption is around 1 amp. The radio is also un detectable as it doesn't have a local oscillator in it, as long as you don't deliberately force it into regeneration. There is also some super regeneration added with the extra coil winding, giving a very smooth slide into detection. The radio should be EMP/CME proof as its valve powered, but the two transistors and 4 diodes in the power supply may be destroyed. Spares are easily replaced as they are only 2N3055 type transistors, and IN4007 diodes, cheaply and easily available from almost anywhere and easily changed out. The valves are very common TV types, used in their thousands in many brands of TV sets from the 60's and 70's and can still be found gathering dust. There are many alternatives to the 6CB6, a direct plug in replacement (with slightly less gain) is the 6BZ6, others include the 6AU6 and indeed almost any pentode type, even the old octals 6V6 etc, will work. The audio stage could be replaced with a 6BM8 (not directly pin compatible), or even with 2 separate valves, such as the 6AV6, 6AT6 for the triode pre-amp and a 6M5 or 6AQ5 or 6BQ5 for the output valve. Obviously, a valve data book is handy, and if you are going to get into this technology, invaluable.
(In the background is my WW2 AR7 communications receiver, also totally EMP/CME proof, powered from 12 volts DC and with the high tension derived from a genemotor, also from WW2.)
Underneath view Top of chassis view View of coils, the short wave coil is double ended and is actually 2 separate coils. Coil winding details are below.
Circuit diagrams follow.
The frequency you are tuned to is read from a simple graph, shown below and linked to the multi turn dial.
Note, it is a straight line as the tuning capacitor I used was a linear type. Most modern types are logarithmic, so the tuning curve will not be a straight line.
The next radio I will post is my all mode, all band bugout receiver.