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About RF Cafe
Copyright: 1996 - 2024 BSEE - KB3UON RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived... All trademarks, copyrights, patents, and other rights of ownership to images
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Operation Radio Airwatch |
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See all articles from Popular Electronics. Operation Radio Airwatch By Morris MosesRadio-equipped helicopter spots Los Angeles Freeway traffic snarls  Chock-full
of electronic and radio communication equipment, a colorful helicopter
prowls above the traffic-congested freeway system in Los Angeles,
California. The roving whirlybird seems to be everywhere at once,
knows in an instant when safety is threatened below, and shares
this knowledge with some three million harassed drivers faster than
you can say, "turn off at the nearest intersection." On call six days a week, 24 hours a day if need be, the trim $50,000 Bell 47-H flies pilot Max Schumacher and newscaster Donn Reed 500 to 2500 feet above the jammed freeway system. Hovering at a standstill, or cruising at 80 miles per hour, the "Operation Airwatch" team transmits reports on traffic conditions to Radio Station KABC which re-transmits these messages on its regular assigned frequency, 790 kc. The driving public keeps its auto radios tuned to KABC for the latest traffic information.  The cockpit of the radio-equipped helicopter. Control box can be seen mounted between two portable receivers. The standby "Handie-Talkie" is kept on the seat.  Pilot Max Schumacher and announcer Donn Reed on the job. Ingenious Equipment. Engineers and technicians at KABC wanted a minimum of controls and switches on the 'copter. Simplicity, economy, and reliability were the technical watchwords. Even though most of the equipment is of commercial origin, there is a feeling of radio ham ingenuity and even "homemade" simplicity about the installation. The link between the 'copter and Station KABC is a commercial General Electric 15-watt FM transmitter and receiver. Units are identical at both the fixed and mobile stations, with the exception of power supplies. The base station is a.c.-powered and the equipment on the 'copter is powered from its 24-volt d.c. supply. The receiver is a G.E. superheterodyne using a triple-conversion circuit, with each converter employing a separate crystal-controlled oscillator. Air Rescues. Police radio calls are monitored with the aid of a converted RCA transistorized broadcast receiver. In between routine traffic guidance, the busy whirlybird has followed the police calls to some very unusual air-rescue adventures. When three teenage boys and a rubber life raft were mixing it up with the Los Angeles River, pilot Max swooped down on the youths and helped push them ashore with a blast from the whirlybird's rotors. Meanwhile announcer Donn gave the radio audience below a spray-by-spray description of the rescue. Other aircraft and landing field towers are contacted with a Lear 108-128 mc. transceiver mounted on the instrument panel. Pilot Max keeps an "ear" on this (as well as on the police call channel), leaving newscaster Donn free to study developments on the complex highway panorama stretching below. Chats with passing aircraft often help the Airwatch crew learn about urgent traffic situations not immediately within their vision. DX'ing Missouri. Just in case the main equipment should fail, a battery-operated, crystal-controlled Motorola transceiver is always kept ready to go. This set puts out about 3 watts at 26.19 mc. and can hold out for about 40 hours of normal operation. The Motorola was the original set used by the Airwatch, and by some freak of transmission is often picked up by Radio Station KFRU in Columbia, Missouri. "We have a regular ritual here of listening to the Los Angeles Freeway helicopter reports" wrote KFRU. Once the G.E. equipment "konked out." On went "Mickey-Mouse" (pilot Max's name for the Motorola transceiver), and just in time; a serious freeway collision had occurred involving an immense truck-trailer and four cars. Traffic started backing up for miles. Newscaster Donn recalls: "Five minutes after I radioed alternate routes, the freeway was so clear of traffic you could have fired a cannon ball down it and not hit a car." Cruising at about 80 mph one afternoon on a routine freeway report "mission," the radio 'copter saw the first few wisps of suspicious-looking smoke. Where there's that kind of smoke at that hour in Los Angeles, there's probably a fire. There was; at a codeine factory. Airwatch reported to the KABC base at 3:50 P.M. The station called the Fire Department. The fire was snuffed out at 4:15. Following the Cars. On weekends the radio watchbird follows seashore-bound motorists to California's jammed beaches. Motorists are given weather reports, visibility estimates, water and air temperatures, and advice on parking problems. At baseball games the 'copter is always welcome, since traffic is particularly heavy. How does the average driver feel about Operation Airwatch? Well, when Max and Donn asked the drivers to turn on their lights one evening, the bumper-to-bumper caravan responded whole-heartedly. Result: the whole freeway system was lit up like a fantastic Christmas tree. And that's a lot of watts. Posted 10/102011 |
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