Building a Doerle Two Tube Shortwave Receiver

My finished Doerle Two Tube Shortwave Receiver!

The Inspiration

I hold a fast pace Information Technology job by day. In the evening and off hours I enjoy building and restoring electronic appliances and devices from a simpler time. One day, while idly browsing Amazon amateur radio books,

I came across this great book from 1938 on how to build four different short wave receivers. What was even cooler is that someone took the time to format it in Kindle EBook format! One click and a Kindle version of the vintage "HOW TO BUILD 4 DOERLE SHORT WAVE SETS" book was mine!

What is a Doerle Short Wave Set?

Doerle "sets" were a popular home built regenerative shortwave receiver of the 1930s. Designed by amateur radio enthusiast Walter C. Doerle of Oakland, California. Doerle's regenerative radio designs were published in many amateur radio magazines in the 1930s. Doerle's Short Wave Set designs were so popular in the 1930s because of the ease of construction and use of inexpensive parts in their design.

Not much is know about Walter C. Doerle or if he was even compensated for the designs featured in the book "How to build 4 Doerle Short Wave Sets" and other vintage publications.

The Doerle name lives on as his shortwave set designs are still popular with Glowbug and Boat Anchor amateur radio enthusiasts of today.

Definitions:

Regenerative Receiver: Type of receiver that feeds a portion of the output signal back to the input, in a positive feedback configuration, in order to boost the amplitude of a radio signal many times.

Glowbug: Term used by amateur radio enthusiasts to describe a simple home built tube-type radio set, reminiscent of the shortwave radio craze of the 1930s.

Boat Anchor: Obsolete tube type radio sets that are so heavy and cumbersome that they could be used as a boat anchor!

It's the 21st Century, can I still purchase vacuum tubes?

Absolutely, there are many vendors that sell vacuum tubes and high voltage electronic components required for vacuum tube circuits. Many musicians and audiophiles even today love the sound of vacuum tube audio amplifiers as they believe they produce a warmer more natural sound. As such, there are many vendors that cater to their vacuum tube needs.

The type 30 vacuum tubes and other components used in the Doerle Short Wave Set I built are available from the two vendors below.
​
Source of Vacuum Tubes and related components

• Antique Electronic Supply
• TubeDepot

Building a Two Tube Doerle Shortwave Receiver Set

Step 1 Source Vacuum Tubes and Electronic Parts

​I found everything required to build my Two Tube Doerle Shortwave Radio set from Antique Electronic Supply (AES), the link to this company's web site was provided earlier.

Step 2 Design and Build Cabinent

The cabinet is made of salvaged wood from shelves that used to hang in my garage. I used degreaser to remove motor oil from the surface. Once degreased and dry, I used a palm sander to smooth out dents and imperfections.

The cabinet for my Doerle Shortwave Receiver is going to be open type. Basically, L shaped with the top piece used as the front panel with all of the controls, and a bottom where the majority of parts are to be placed.

The shafts for the Tuner, Regeneration, and Filament controls are not long enough to protrude through the front of the 3/4 inch wood. So I decided to carve out areas in the wood so that the shafts could protrude through the front.

Next, it was time to layout the parts on the front panel and bottom of my Doerle Shortwave Receiver. I then mount parts with screws and checked for fit and placement.

I used tape to mark the depth of holes I want to drill so as not to drill right through the wood.

I used a Wooden Hole Saw Set to drill concentric holes 1/2 deep into the back of the front panel.

I then used a screwdriver like a wood chisel to remove the remaining wood between the concentric holes drilled by the Hole Saws.

This is how the back of the front panel looks after the remaining wood was removed from the indentations created. The indentations were then sand to remove any roughness.

​I created a paper template to be used later to plan out the wiring.

Time for two coats of polyurethane with light sanding between each coat!

I glue aluminum foil, the same type you use to wrap food in, to the back of the front panel. Elmer's White Glue works fine. This foil will be tied to circuit ground in order to reduce the effects of hand capacitance during operation.

Finally, some rubber feet on the back side of the bottom panel.

​Step 3 Final Mounting of Electronic Parts

It is easiest to mount the variable capacitors and variable resistor to the front panel first!

​Finally, you can mount the hardware on the bottom panel.

​Step 4 Wiring

Creating a wiring diagram a head of time makes wiring easier.

Here is my Doerle Shortwave Receiver ready for wiring.

First, I wired all of the ground connections (Black wires).

Next the 90 Volt circuit (Purple wires)

Followed by the tube filament circuit (Red wires).

Finally the 45 Volt and Tuning circuits (Yellow and Blue wires).

​Step 5 Winding the Coils

The coil that is part of the tuning tank circuit, and the regenerative coil, are mounted to a removable 8-pin octal base. You plug in different coil assemblies into the octal socket on the bottom panel of the radio to change Shortwave Bands.

Here is a picture of the coil assembly for the 15-45 Meter Bands.

Next you have to scrap off the varnish insulation on the 22# magnet wire in order to prep for soldering.

Next you feed the bare part of the magnet wire through the proper pins and solder.

Here is top view of the coil assembly.

Finally, check each coil's continuity at the pins.

​Step 6 Final Prep

Install the Type 30 Triode Tubes, plug the coil into the socket, label connections.

In addition, label the front controls and headphone connections.

​Step 7 Obtain Suitable Power Supply

In my "Battery Box", I use two D batteries for the 2 Volt filament voltage. I connect many 9 Volts in series to obtain the 90 and 45 Volts needed to power the receiver.

Fahnesstock Clips on the back of the "Battery Box" provide access to the required Voltages.

Connect the Doerle Shortwave Receiver to a suitable power supply, antenna and ground. I use my external G5RV Amateur Radio antenna and main water pipe that comes into our house as a ground. In addition, connect high impedance headphones to the front.

​Front view showing the Tuning, Filament, and Regeneration controls. In addition, connections for headphones.

​Step 9 Testing

Set the Tuning, Filament, and Regeneration controls to mid position. You should hear atmospheric "hiss" from the headphones, once the power supply, antenna, and ground are connected. Use the Tuning knob to select AM broadcasts. Once selected, adjust the Regeneration control counter-clockwise to the point of where you hear oscillation, then turn it clockwise slightly until the oscillation stops and the AM broadcast is clear.

​This is the point that the Doerle Shortwave Receiver is at maximum gain. Turn the Regeneration control further clockwise to reduce receiver gain if the AM broadcast is overpowering the headphones. The only time you should need to adjust the Filament control is if your A+ batteries is getting weak. Adjust the control until there is 2 Volts at the filament pins of the Type 30 vacuum tubes.

​Troubleshooting

Here are some troubleshooting tips if your Doerle Shortwave Receiver is not working as expected.

No sound from headphones:

• Check wiring with power source disconnected.
• Connect power source, check Voltages at the power terminals of the Doerle Shortwave Receiver to make sure they are correct.
• Turn out the lights and make sure the filaments of both Type 30 tubes are glowing.
• If using a Crystal type headset or earpiece to listen, attached a 47K 1/4 Watt resistor across the headset leads to ensure the proper current flow.
• Make sure you have high Impedance headphones connected to your Doerle Shortwave Receiver. The Impedance must be at least 5K, common 8ohm headphones will not work.

AM Broadcast are weak, Regeneration control does not have any effect:

• Switch the two Type 30 Vacuum tubes, I found that one tube worked better as a RF Amplifier/Detector while the other Type 30 Vacuum tube work better as an Audio Amplifier. Remember, these vacuum tubes are over 85 years old!

​Conclusion

This was a most gratifying project. When not in use it is proudly displayed on a shelf in my basement "Man Cave". Building a Doerle Receiver is a great way to learn about electronics past.