Presented below is what I see is a good starting place to begin our Vacuum Tube type Regen Receiver Project.
I make that statement as Mike, W3IRZ the designer has struck Gold! Firstly, the 6BA6 tubes are plentiful and low cost and secondly the whole shooting match operates off of 12VDC. No exotic high voltage circuits here! There are few components and some great suggestions for the choke substitute. The 1 Millihenry choke can be fabricated from a T-82-43 core with 46 Turns of #24 wire. A 2.5 Millihenry Choke is 73 Turns of #26.
Note this came from a 1999 Posting by W3IRZ.
I have been unable to find him in QRZ.com. Maybe a SK.
The steps from here on include the following considerations. This is like the YL wearing two sets of Knickers problem. Hint: The critical path is getting through the 1st set.
First look at the schematic and immediately you see few components and absent is the often-seen tickler coil feeding a signal out of phase in the plate circuit... Jimny Cricket this will oscillate and that is what you want. The 50K pot is the regeneration control.
The unknown path traveled is always made easier when you have a road map! Such a road map exits on the WU2D's (Mike) You Tube Channel as he has extensively covered Vacuum Tube Low Voltage Receivers. There I learned about the Morgan Regen Receiver which likely was the Bitx40 of that era.
An interesting factoid in one of Mike WU2D's regenerative receiver videos is that the midpoint on the pot's travel is the sweet spot. Less or More pot travel beyond the centering indicates you have too much or too little feedback. The schematic says 3/4 of a turn from the cold end (ground). At the outset finding the right spot is the same issue as getting through the 1st set of knickers. Translated this is experimental.
Regens are notorious for responding to hand capacitance and there must be no movement of components like the tuning coil. Failure to address these two issues will result in the project not being a regen receiver but a Theremin Musical Instrument... she will howl!
WU2D reflects on this issue with some solutions such as a metal front panel and even though the receiver is built on a wooden board, the board underside is an aluminum plate where ground points pass through the wood to the metal plate.
My design will use a chunk of PC Board that will in effect provide that ground plane on top of the wooden board. The front panel will be aluminum and that will be mechanically fastened to the copper PC Board. Bracing will be fitted to the front panel so there is no flexing of the front panel as you tune the Regen. It is considerations such as these that determine the difference between it sort of works to a receiver that does work.
The next installment will cover translating the schematic for the 6BA6's to island squares (or Manhattan Pads). Once there we can pick off reference points for the CNC sketch (or where to glue pads).
There is hope that others in the homebrew community may take on this project. Another bonus is that you could directly sub 12BA6's and use two twelve-volt batteries in series as a power supply. Lots of flexibility for parts substitutions.
Them that know can make it go but those who don't wished they did.
73's
Pete N6QW
