The "Sky King" Solid State Regen Radio

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FET regen radio
"Sky King" Model N5348A Regenerative Radio
Coverage is from 500kHz to 20 MHz

Evolution of the radio.

On October 8, 2014, a guy named Greg emailed me out of the blue. He included seven attachments in the email. Some of them were plans for  a regen "Twinplex" radio from a Lindsay publication. He wrote "Enjoy, let me know how it works out for you."

I didn't get around to playing with the circuit 'til the middle of January, 2015.

radio schematic
The schematic Greg sent me.
I altered it to receive the AM broadcast band.
radio coils
The article said to use a toroid coil form but I didn't have any. I tried two straight ferrite rod type coils but they didn't regenerate well.

regen radio

I used a plug-in coil made by Elmer Osterhoudt. The results
were pretty amazing considering there was only one transistor.

radio coil in Polyurethane

I decided to use the same type of coil that is
used in the Peebles Two Tube Regen Radio.
radio coils
Antenna tuner coil on the left. It would eventually be discarded. The main coil is on the right. The red winding is for the RF amp but
it was also discarded. The top winding on the right hand is the "tickler" coil which was eventually rewound.

Here's the first version of the radio. A Mike Peebles antenna tuner and an external amplifier were used, and I tuned to a corny old song for the movie. There is no RF amp.

The problem with the above setup is that you can't get your hands near it or it throws off the regeneration. Or looking at it another way, once you tune in a station, don't take your hands off the knobs!

The next idea was to use the Lindsay "Twinplex" circuit to build a solid state version of the Peebles Two-Tuber, with the antenna tuner and amplifier on a single chassis.

radio layout
It was time to make a setup that would be easier to work with, but semi-permanent so it could be changed.

                                         ...Therefore the front panel was made of cardboard with aluminum tape as a shield.

          In these pictures the audio amplifier has already been built. I ran into trouble with this very board while building the Ferrite Ferret
          and this working unit was left over from that project.

radio parts layout
Main parts mounted on the base.

mounting a variable capacitor
mounting a variable capacitor

While mounting the variable caps I pushed the stator plates of one of them out of alignment. I thought I was being careful by adding
washers to the bottom, but I used the wrong size washers. Fortunately the plates can be adjusted by tapping on the plastic plate holders.
mounting a variable capacitor
There is now a space between the stator plate brackets and the base.
pictorial diagram
FET detector
I drew pictures of how the parts should be mounted, then followed the pictures. That way I didn't screw things up.

Notice the 2.2K resistor on the source of the transistor. A guy named Garry wrote that the 1K resistor in
the schematic was too low a value. Sure enough, changing it to a 2.2K improved the set. Thanks Garry!
parts mounted
shaft extensions
The audio amp and DC filter went in first. Home-made shaft extensions.

regen radio layout
At this point the basic radio is completed and it was time to fire it up. Was everything soldered correctly? Will it work?