Anyone interested in old (PDP-8 driven) Radio Automation hardware?

Dale H. Cook radiotest at
Wed Dec 9 10:30:28 CST 2015

At 10:05 AM 12/9/2015, wulfman wrote:

>Before one opens ones mouth its best to become informed.

I have nearly forty years of experience as a radio station chief engineer, and began doing radio engineering in college in 1969.

>yes we had 4 track nab carts

Wikipedia, as is so often the case, is misleading. The Muntz Stereo-Pak system was not an NAB standard system, and never caught on, in part because the frequency response was less than that specified by the NAB standard and in part because the moving head system was problematic to keep operating properly. Because the carts were not NAB standard they could not be used with the NAB standard cart machines used in broadcast studios. See the 1976 edition of the National Association of Broadcasters publication "NAB Standard: Cartridge Tape Recording and Reproducing." Section 1.2 of the standard specifies "The Standard requires either one program track and one cue track for monophonic programs; or two program tracks and one cue track for stereophonic programs."

The multi-cart playback systems that were NAB standard and were most often used in radio automation systems were:

1) Carousels and their variants (such as the IGM Go-Carts) which had one set of fixed-position heads with electronics, and could move a group of carts so that the heads engaged one cart at a time.

2) IGM Instacarts, where every cart was stationary and each cart had its own set of heads and electronics.

Carts from either of those systems were the same as those used in studio machines. If an automation system failed the station could be manually operated with an announcer manually activating the reel-to-reel decks that held the music and manually playing the carts in the studio cart machines. For one of the last of the tape-and-cart based automation systems that I took care of (an IGM 770 system in the 1980s) the station purchased a pdp8/m from a used IGM system. I trained the station operations manager in how to swap out the minicomputer and get the system running again, so that announcers need only run the system manually for about 45 minutes after a failure. I lived more than an hour's drive away, and if already working on an emergency at another station might take some hours to respond, so reducing IGM downtime was a big advantage. When I did get there I repaired the defective pdp8/m and put it back on the shelf. Other failures, such as failures in an Instacart or in a reel-to-reel deck were not crippling, as there were multiples of both, but failure of the pdp8/m would halt the system.

Dale H. Cook, Radio Contract Engineer, Roanoke/Lynchburg, VA 

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