One current dream project is to build a low voltage miniature tube multimode
receiver, transmitter, or transceiver for AM/CW/DSB but it seems more likely that
I will convert an existing portable rig to miniature tubes.

I looked for information about the 3A5 tube and found lots of stuff! (see below)

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

Minimalist 3A5 80M CW Transmitter

Minimalist 3A5 CW Transceiver

Another Minimalist 2-Tube 3A5 CW Transceiver

Home page for Two-tube 3A5 CW Transceiver

Four-tube 3A5 & 3D6 CW Transceiver

Four-tube 3A5 & 3D6 CW Transceiver

Minimalist 3A5 AM Transceiver (sorry, cannot translate notes)

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 transmitt 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

MORE RELATED DISCUSSIONS

"QRP Xmtr Tube Choice"

"American Miniature Tubes for Radio Receiver"

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

12V Space Charge Tubes

The goal is, therefore, an amalgamation of all of the above into a functioning
AM/CW/DSB transmitter or transceiver using multiple 3A5, and similar, mini-tubes.

Can I do this with No Solid State Devices?
Do I Need to use the IN4148 Double Balanced Mixer,
or is there an alternative DBM using a 3A5 or similar?

Design Pending & Suggestions Welcomed!

AZDEN PCS-3000 12-PIN MIC PINOUT

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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