Modulation Monitors

Although it’s a relatively esoteric subset in the world of vintage broadcast equipment, no engineer could properly do his or her job without a scope and a modulation monitor.
I’ve been fortunate to obtain some beauties over the years, so take a look and enjoy.

General Radio 1931-A

Gates M-5693

This beauty is still in operation in my shack. It’s near a 10 cosmetically and it works perfectly. You see some 75 meter RF from my T-350 XM with no audio. Built around 1948, it was the most common monitor in use in BC stations through the fifties, at least.

Circa 1959, this unit went with many Gates “package” set-ups. As new stations came on the air, owners of start-ups could order an entire basic radio station in one package. This unit featured improved ballistics and peak monitoring as the rock and roll loudness wars began. This unit is in excellent cosmetic shape.
I always thought it was a bit too complicated to keep properly calibrated, but I’m glad I own one now.

RCA BW-66E

RCA’s classic from about 1955. Simple in design and a real workhorse. This one needs some work but the front face is in excellent condition.

CCA AMM 1-D

You would have found this faithful monitor in BC stations beginning in the mid-late 70s. When switching from positive to negative modulation, the disc jockey would hear a “pop” when the engineer fooled with it in the transmitter room. Engineers hated disc jockeys, so you figure it out. This one is in fairly good shape but some smoke has been let out.
What’s that riding on top? It’s a black-face AM-80 in perfect condition. I really shouldn’t allow a solid- state monitor to defile one with tubes.

General Radio 731B

Here’s a real diamond in the rough, the predecessor to the 1931A monitor circa 1939. This will be a total rebuild and a labor of love. I hope it can be restored so it can monitor the Western Electric transmitter from the same era.

For questions please contact KT4NO