A Safer Ham Radio Rig Concept for Agent Sonya from 1936: You Know, With Tubes and Batteries

One consideration that I hear often with relation to vacuum tube circuits is to be very, very careful of the high voltages that are typically involved.

And, I completely agree.

What if the highest voltage was 45 V though? A battery operated rig would seem more useful to Agent Sonya in my opinion. I went searching for something that might take less voltage, and therefore be safer for construction by the gang and I. It didn't take too long to find something that might work as a basic concept, although I do understand that the operating frequency of the circuits shown below wouldn't transmit long distances.

Here are the schematics from the 5 meter rig outlined in the March, 1936 issue of Radio Craft on page 525

Notice that at first glance, the highest voltage involved is from a 45 V battery. The 'interruption-frequency' coil concerns me a bit because I don't know what it's for yet, and it looks like a transformer.

Upon further reading, and squinting at the acronym for 'interrupt-frequency' I.F. I believe that 'transformer' might be part of a permittivity tuned oscillator! How cool! Here's how the construction of the coil is laid out:

"The receiver differs from the transmitter only in that an interruption -frequency coil is used instead of the "mike" transformer. This is wound on a form made of fibre washers on a brae screw. The center washers are 5 /16 -in. in die. while the large ones are l;a -in. The space for the secondary is ?a -in. wide. while that for the primary is 1732 -in. wide. The wire is N.,. 34, enamel -covered and the winding is easily done if the screw which holds the form together is held in a hand drill, the drill in turn being held in a vise."

It turns out this was not part of a PTO. It's a transformer that couples to the headphones.

"The receiver is quite simple to set into operation, the only trick being to secure proper super- regeneration. This is governed entirely by the I.F. coil, and by the condenser C6 across the secondary. If a low -pitched buzz is heard in the phones, more capacity is needed across the secondary. Operation of both units is simplicity itself. Just snap the switch, and tune. The hiss of the receiver will disappear when a strong signal is tuned -in. "

I wonder if this similar to the hiss mentioned in the DC Receiver project over at Soldersmoke.

I also wonder if interrupt-frequency was a typo in the magazine?

It is not! The concept of interruption frequency is mentioned in relation to super-regnerative receivers in the 1934 ARRL handbook on page 132. I'll need to look into this further, because I'm out of time today.

This is not the exact microphone transformer mentioned, but its advertisement appeared in the May, 1936 issue of Electronics

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Copasetic Flow

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