Back to the future!

Folks have asked me about my 6L6 Colpitts-oscillator transmitter that I use on 80 and 40 meter CW during the Antique Wireless Association on-the-air tests. It's a replica of a 1938 transmitter.

Here's a photo of the little rig. It was built on my kitchen table during a time when I was a cliff dweller in the mid-1980s.

The transmitter uses a glass 6L6 (so you can enjoy the glow of the filament), and a VR-150 voltage regulator tube (its gas glows with a nice purple hue). The DC power is derived from a Type 80 full-wave rectifier tube.

The rig is crystal-controlled, with band changes made through the use of plug-in coils. It develops about eight watts of RF.

This rig, and its companion receiver, along with a vintage schematic and Mac key, were featured in QST Magazine, December 1997, pg. 20.

Here's a view of the innards of the 6L6 rig.

Some concessions to modernity were made in its design. For example, although it uses plug-in coils, the tank circuit is part of a pi-network. That permits easy matching to 50-ohm unbalanced transmission lines.

For the same reason, a standard SO-239 coaxial output connector is used, as well as an old TV-style power transformer. Likewise, the rig includes an indicating fuse holder, and modern tubular high-voltage electrolytic filter capacitors.

When signing off, I usually wave my hand over the 6L6, "wobbulating" the rig's frequency for a unique final note!

This is a view of the guts of a companion receiver to the 6L6 transmitter. It is a replica of a "schoolboy's" regenerative set that was popular in the late 1920s through the 1940s.

Like the transmitter, band changes are effected by installing the appropriate plug-in coils.

The regenerative tuner uses a Type 24 pentode tube. It's followed by a Type 27 triode audio amplifier.

Here's a view of the receiver's front panel. Simple enough, eh? There's just a tuning knob and regneration control.

Nonetheless, there is a bit of a technique that you need to learn to set the regeneration at the right point and get the receiver to play.

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Click here to review the 6L6 transmitter's schematic.

Click here to see the regenerative receiver's schematic diagram.