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International Tapetronics Corporation's 850 debuted at the 1977 NAB convention, held in Washington, DC. The 850 featured differential braking, a push-button tape marker and a playback/record synchronizer. Differential braking stopped reels smoothly without slack or risk of tape damage. The playback/record synchronizer allowed users to record on one channel and listen to another in complete synchronization.

A high-friction polyeurethane roller pulled the tape with less pressure, resulting in less wow and flutter. The keyboard configuration allowed eyes-off, hands-on “touch system” control, and the record key was double spaced, preventing the operator from pressing it by mistake. The hinged lid would lift back for access to the entire head assembly. The unit also featured a half-inch thick hardened aluminum deck and was warp-proof.

That was then

When several class 1A clear-channel AM stations signed on in the ‘30s, RCA-50B transmitters were a popular choice. This photo, taken around 1935, shows the installation of a 50B at KOA, Denver. This installation was typical of many stations at that time. KOA was owned by NBC, which also owned 50kW stations in Chicago, New York and San Francisco. Many of these transmitters remained in operation until the ‘60s. The 50B transmitters were manufactured for RCA by the General Electric Company and the Westinghouse Electric and Manufacturing Company.

The 50B transmitter consisted of a 50kW linear amplifier using two water-cooled UV-862 tubes in a push-pull circuit, which was driven by an RCA-5B 5kW transmitter. The transmitter had four main units: (left to right) the 5kW driver transmitter, the 50kW linear amplifier, rectifier cabinet and control panel.

While the transmitter room layout is typical of most 50B installations, the patterned glass ceiling is not.

Transmitter information and photo courtesy of John Byrnes from his website at

Sample and Hold

Year Attendance















A look at the radio industry
NAB Convention Attendance
A slow decline after a peak in 2000

Source: NAB
* - Anticipated figure. Official number has not yet been announced.

BE Radio is looking for the oldest transmitter in daily use. Do you think you have it? Tell us about it by sending an e-mail to; include your name, station call letters, make and model of transmitter and the year it was installed.

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