Knight-Kit Wireless Broadcaster

Knight-Kit Wireless Broadcaster

While hardly a boatanchor, this Knight-Kit Wireless Broadcaster was a fun piece for many experimenters. It was sold by Allied Radio as a kit. The working unit allows the user to broadcast a limited-range signal from a microphone or phonograph. It will also work with a line-level input from a CD or cassette player. Great for sending period music to your old (and new) broadcast-band radios. The tuning capacitor allows setting the broadcaster to an unused frequency from 600 to 1600 KHz.

Antenna length is limited by FCC rules to ten feet. Experimenters in the 1950s tended to stretch this limit a bit :-) Check out the stories from those who built these back when. The following site by Jim Addie specializes in the Wireless Broadcaster. His site has some stories by those who built and used these little gems. See also the story below.

Knight-Kit Wireless Broadcaster

There were two versions. This version with its fully-enclosed chassis was the later one. It was reviewed in Popular Electronics magazine in June 1959 pages 101-102. It has an output transformer that can be hooked to a speaker for use as a low-power audio amp. (The article links are to SMECC, the Southwest Museum of Engineering, Communications and Computation.)

The earlier version, which had an open chassis, was reviewed by Popular Electronics in May 1955, pages 31-33 and 111. It uses a choke in place of that output transformer. Both versions use a 50C5 tube as an oscillator with another 50C5 for Heising modulation. A 12AX7 is used as the audio preamp. These are AC-DC circuits. Although this circuit uses "floating ground" (a resistor and/or capacitor between the metal chassis and the power line), an isolation transformer is strongly recommended for safety. At the very least use a GFCI outlet.

Since most of the parts are still available, a home-brew version of this little transmitter, with some circuit modifications, could make a nice little minimalist 160 meter AM QRP rig. Yes, licensed hams can use antennas longer than 10 feet, at the proper frequencies. "Rig here is a phono oscillator circa 1959."

PDF copy of manual for the Knight-Kit Wireless Broadcaster originally from WE0H but now by way of the web archive's "Way-Back Machine"(7.3 Mbyte file)

Memories from users of the Knight Broadcaster

The Knight broadcaster was a favorite for many teen-age electronics enthusiasts. Here is a note from Terry D. who apparently plate-modulated the broadcaster via an external audio amp (and used a longer antenna!)

And a note from Bill R.

And thank you, Bill. Our hobby activities have led many of us to rewarding careers.

Here's a note from Dave KG4GTI who used the "home broadcaster" circuit in the transformer powered Knight 6-in-1 Lab kit. If you have the 6 in 1 booklet or the circuit diagrams, please send me a copy. I have the schematics for the three-tube 10-in-1 but not the 6-in-1 which uses just one tube, a 6SN7.

Knight-Kit 6 in 1 Lab kit catalog ad

Thank you Dave and best wishes with continuing the music.

Thank you John. That cardboard RCA is an interesting piece as well.

Did you have some interesting youthful experiences with the Knight or other Broadcaster? Send an e-mail. See the home page for the address.

1-22-02; updates 6-04, 4-08, 12-09, 2-14, 6-15, 1-20

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