A Five Tube Regenerative Receiver

This is a five tube regen. that provides reception from the broadcast band all the way up to the higher shortwave bands by just changing one plug-in coil. 



Front view showing the nice vintage dial with the fleur de lis, which is the symbol of Louisville.   The front panel is 1/8 inch aluminum and the speaker opening was cut out with a scroll saw.  The control on the bottom left is for regeneration and the one on the right is for volume.  I already had the power supply on the right, which works great with this receiver.   Click Here for a printable schematic.  First save the file to your computer then print it in landscape mode and size to fit the full page.




Rear view.  I wanted to use mostly metal tubes, as these are my favorite.  The design was dictated by what tubes I had on hand.  I ended up with a 6SF5 triode (far right) for the RF amp. followed by a 6SJ7 pentode (middle) for the regenerative detector.  I used a 6SK7 pentode (left middle) for the audio amp. because of the high gain.  For an audio output, I used a 6K6GT (far left).   I used screen grid voltage to control the amount of regeneration.  I regulated the B+ with a 0C3 (beside speaker) down to 109 volts then further dropped it to 38 volts to provide a stable source of control voltage. Notice in the schematic, I used a single tapped winding in the coil circuit as opposed to a tickler feedback.  I used this setup because I would only need 3 pins on the coil socket.  I could then use the other pin to cut in and out a capacitor which decreases the tuning capacitor value when using higher frequency coils.  On lower bands such as the broadcast, the coil has a short which bypasses the capacitor and allows the whole value of the tuning capacitor to be used.

Another AMSCO straight line frequency variable capacitor was used for tuning.






For the coil construction, I used 1 1/2 inch diameter four pin plug-in coil forms.  The coil on the left covers the broadcast band from about 560 to 1700 kc. with about 130 turns of # 30 SCC tapped 4 turns from ground side.  The coil on the right covers 4.5 to 7.5 mc. with 21 turns of # 24 DCC tapped at 2 turns from ground side.  As for the coil in the middle, I haven't finished it yet.  I am shooting for coverage somewhere between the other two coils.  There has been several coil winding articles published with varying data.  Like all of these circuits, you will have to experiment.  I could make a set of coils for this set and document the construction and frequency coverage, but if you built your set slightly different, then my coils would be off frequency.  Build your radio first then make the coils to work properly in it.  The information given here should just be a guide.








View of the under side of the chassis.  When I built this, I was in short supply
of 1/2 watt resistors.  I did have a large stock of 1 and 2 watt which I installed instead.  At least I won't be having any resistors over-heat.



The power supply is one I built earlier, so I didn't include a diagram.  It has an octal socket on the back that allows me to plug in other projects.  It's just a simple full-wave rectifier into a pi filter.  The resistor is a bleeder for the B+.  I could have built a similar supply directly onto the receiver chassis if I rearranged the parts somewhat.  I have left the power supply up to you.

The performance of this set is amazing.  The screen grid control of the regeneration is smooth and there's enough volume to blow your ears off!
Selective is great and the sensitivity is so good that I can receive several shortwave stations with no antenna at all connected!

Build one yourself.  Use what tubes you have on hand.  Worst case, you might have to change the bias here or there.  Experiment!  How about multi-function tubes?  Space charge tubes?  Could you add AGC?

Let me know how yours turns out.

Mike




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© 2006 ~ Michael R. Starcher ~ All Rights Reserved