Re: [IRCA] Off the wall question

[Patrick Griffith <antennawizard@xxxxxxxxxxx>]

In one of my previous careers I served for over 12 years as a 911 dispatcher in two states. My first dispatch job was in Rockford IL in the late 70s where I fondly remember the long wire antenna running between the old police headquarters roof and the roof of city hall at the opposite corner of the block. I was told that this was the antenna used for the old AM transmitter which had been located on the roof of the police station. The antenna wire was a heavy looking mutli-strand cable and the insulators at each end looked to be about 2 feet in length. The Rockford police went on the air in 1933 and converted to two-way radio in 1940. Several years ago I researched some of the history of police operations in the AM band. The Galvin Manufacturing Company of Chicago (Motorola was their brand name) realized that many police departments were ordering car radios from them for use in their police cars. Recognizing a market for a police specific product in 1936 they introduced a spe!
 cial receiver called the Motorola Police Cruiser. It was capable of receiving from 1550 kc to 2800 kc. One of the primary differences from the Motorola car radio was that the police receiver was crystal controlled for frequency stability on a specific channel. At this time Galvin was having trouble meeting the demand for its very popular Motorola car radios. So initially the police receivers were only produced on weekends so as not to disrupt normal car radio production during the week. By 1936 Galvin had introduced an AM mobile transmitter operating in the 30-40 mc "UHF" band to enable police cars to talk back to the dispatcher via radio. In the 1920s and 1930s many police departments in the US broadcast on 1712 or 1714 kc. There are reports that at night these channels were so busy that the various police departments across the country had to take turns broadcasting. Some of the early police transmitters sent Morse code messages instructing individual squad cars to respon!
 d to a call box to get their message via telephone. As early as 1921 t
he Detroit police had a mobile radio system. The transmitter had the call sign KOP which some attribute to the origin of the word "cop" as a slang for police officers (most likely "cop" is a shortened version of "copper" resulting from the common use of copper badges many years before the Detroit radio system existed). The Detroit system operated on 1050 kc and later was moved to 1080 kc. Some exceptions to the 1712/1714 kc frequencies that I noted were Berkeley CA on 2410 kc, and most radio equipped departments in the state of Tennessee on 1619 kc. A history of the Denver police radio system indicates that they operated on 1610 kc. That history mentioned that this was a common nationwide police frequency as well and mentions Denver police cars relaying messages at night between various western US police agencies. Relays between Indio CA and Kansas are specifically mentioned. It also mentions that the Grand Junction CO police were on this frequency as well and came in so cle!
 ar that Denver officers sometimes responded to calls with similar addresses that were actually intended for Grand Junction officers. I found a reference stating that in 1949 the FRC (pre-FCC) ordered all law enforcement stations to move to VHF. However, it appears that it may have taken years for this move to be completed. Here are some early police radio call signs taken from various historical references: KOP Detroit, KGPX Denver, WPGD Rockford IL, WLAW New York City, WMAZ Indianapolis, KSW Berkeley, WPDA Tulare, KGJX Pasadena, KGPL Los Angeles, KGPI Omaha, KGZY San Bernadino, KGPC St Louis, WPDB WPDC WPDD Chicago, WRR Dallas.
 		 	   		  
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