[Lowfer] A self-rectifying transmitter

[John Bruce McCreath]

> I have never heard of a self-rectification oscillator before.

Hi Johan,

From what I’ve read about them, they were employed as emergency
transmitters on board ocean going vessels during the late 20’s and
early 30’s.  Apparently 400 Hz. power came from a dynamotor, since
most ships of that era had 220 volt D.C. power

I found the circuit in one of my old college textbooks and I was curious
to see if I could build one.  The two tubes are in parallel with all of their
connections, except the plates.  Each plate has its own D.C. blocking
cap and RF choke.  The hot leads of the HT supply connect to the RF
chokes and the centre tap goes to the common cathode terminals.

My source of 400 Hz. power is from my J2E audio oscillator, which is
quite powerful, going up to 40 volts on its 600 ohm output terminals.
I used a 1:3 step-up transformer to get the 120 VAC which was then
connected to the primary of the power transformer for the transmitter.
If I plug the transformer into the mains, I get 60 Hz. modulation that
sounds awful, but with 400 Hz. it’s quite nice!

73, J.B., VE3EAR

LowFER Beacon "EAR"
188.831 kHz. QRSS30
EN93dr