[John L Stewart]

Aw Yes, the wondrous Wobulator!

Patrick mentioned a very useful piece of test equipment. I built one around 1956 to be used to align IF Transformers in AM receivers. To avoid the mess of mechanically wobulating, the circuit used a reactance modulator.

Tuneable over the range of 450 to 475 KHz with a regular variable cap to go to the IF center frequency, the reactance circuit driven by a handy sine or triangular wave oscillator did the rest.

The sine wave also drove the X-axis of a scope rather than the internal timebase. A plug-in slot, such as an octal socket provided a place where a crystal of say 465 KHz could be plugged in. That way a birdie showed up on the display to indicate mid-band.

The schema is long gone. Think it was published in Audio Magazine. It used a 6BA7. But I expect a search on the web would find something.

Cheers to all, John