Project Page, Resources, and Schematics


Dentron Clipperton L Amplifier

Elmac AF-67 160-10M Transmitter

Heathkit HP-23-A Power Supply

RCA WR-67A Test Oscillator


Homebrew 6M Delta Loop

Yaesu FT-957D Portable Station

Lots of Low Voltage Tube Information

"Pencil Tube VFO"

"American Miniature Tubes for Radio Receiver"

3A5's, Space Charge Tubes, Regens, etc.

12V Space Charge Tubes

12V Space Charge Tube Receiver

12V Space Charge Tube Regen

12V Space Charge Tube Mod for an AA5 Receiver (scroll down)

12V Space Charge Tube Receivers with Transistor Audio Outputs

12V Space Charge Tube Discussion

Battery Tube Discussion

Pencil Tube Pictures & Data

Low Voltage Tube Audio Pre-Amp Kits

24VDC Tube Amp

Low Voltage Tube Kits

Military Gear Discussion - Subminiature & Pencil Tubes

Dual - Sub-Miniature - 6088 Franklin VFO

3a5 Single-Tube Tx/Rx

KF9CM also shows a 6sn7 Single-Tube Tx/Rx

Click here for a discussion of usages of 3A5's

Home page for Two-tube 3A5 CW Transceiver

Four-tube 3A5 & 3D6 CW Transceiver

Minimalist 3A5 6M AM Transceiver (Automatic translation via next link, below.)

Click Here for the Home Page & Discussion of the 3A5 Transceiver circuit above.

After all of that I THEN stumbled on this interesting circuit.
(Click to View Link, then return. My discussion & selected text from the article follows below.)

I was interested to observe that his modulation design allows for carrier suppressed DSB or AM.
I am thinking that I may borrow that design for my mini-tube transmitter so it may do double-duty
(actually triple AM/CW/DSB). [Webmaster]

"The output of the DBM contains only the product (of audio and carrier) frequencies.
The DBM suppresses both the input signals and produces double side band suppressed carrier
(DSBSC) at its output. However, since the diodes used in the balanced modulator are not fully
matched, the output of the DBM does contain some residual carrier. This is known as carrier
leakage. By adjusting the 100 ohm preset VR2 and trimmer C7 you can null the carrier leakage.

"To receive DSB signals you need a beat frequency oscillator to reinsert the missing carrier.
If you don't have a beat frequency oscillator, or want to transmit only AM signal, adjust
preset VR2 to leak some carrier so that you can receive the signals on any ordinary radio
receiver. In AM mode 100% modulation can be attained by adjusting preset VR1 and VR2."

I also happened upon a simple conversion for the venerable military surplus BC-696
transmitter from AM to DSB. It is a readily reversible conversion. (see below)

DSB Conversion of BC-696 Transmitter. Page 1

DSB Conversion of BC-696 Transmitter. Page 2

BC-696 Transmitter Schematic



1 Green (K2)

2 Red (Ground)

3 Blue (AF Vol.)

4 Yellow (K1)

5 Purple (K8)

6 Grey (Key Lock)

7 Black (R0)

8 White (13.8V)

9 Brown (PTT)

10 Orange (R2)

11 Shield (Mic Ground)

12 Pink (Mic Out)

R0-K1 = 5K Up

R0-K2 = 5K Down

R2-K8 = Call M1

R2-K1 = MHz Up

R2-K2 = Band Scan

R0-K8 = M Write

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