Topband: Good valve homebrew rig

[Roger Kennedy]

Hi Annas

Having built several Transmitters and Receivers, Valve ones are SO much
simpler (less stages required) . . . and they usually work straight away !
(unlike Transistor ones, where there's often issues to sort out). Plus no
PCBs needed, all the components just hang off the Valve bases, mounted on a
chassis.

A valve CW Transmitter for 160m is VERY simple . . . the VFO is on the
signal frequency, and just two valves will give you ten watts - ECF80
VFO/Buffer, 5763 PA. Add a 6146 or 807 and you will have 100 watts input (80
watts output, as Class C)

If you want to make Transceiver, then you will have to have a VFO on a
different frequency and Mix (so the Receiver is a Superhet) . . . but the
advantage with 160m is that you can have Single Conversion from 455 kHz, so
it's easy to make a stable VFO around 2.3 MHz.

You'd just need to find a nice cheap second-hand 455 kHz CW Filter . . .
copy some of the Receiver stages circuitry from any Valve Rx (R4B, FR400,
etc) . . . so something like a 6BW6 RF stage, 6BE6 Mixer, a couple of 6BA6
IF amps, and an ECL86 Audio Preamp/Output valve. Plus a 12AT7 as a Carrier
Osc and VFO.

On Tx you simply use most of the same circuits in reverse, with a similar
output stage as outlined for the Tx above.

I built a few SSB Transceivers in the 70s using that kind of circuitry . . .
but a CW one is simpler as you don't need a Mic Amp or Balanced Modulator,
and you don't lose any Tx signal through the Crystal Filter (as you'd bypass
it)

73 Roger G3YRO