Radio Technique
A LEADER RETIRES. Bob Aberle-past chairman of the AMA Frequency Committee, prolific model designer/builder/tester, and Technical Editor of Flying Models magazine for the past 15 years-has retired from writing for model magazines. He has not retired from working for a living as a manager in a large aerospace firm. Bob is one of my best friends, and I can testify that he put more time and effort each and every week into being FC chairman, writing, and photography than most people put into the jobs that pay their way through life. That's what filled a file cabinet at AMA HQ, and made his writing good enough to earn the McEntee medal from the WRAMs.
Radio Technique
BIG NEWS: Polk's is now moving toward an all-PCM line for its radio gear. This has to be a good move, because PCM offers better performance on several levels: 1) PCM makes a significant improvement in resistance to all forms of interference. This is due to the way that the computers in the PCM receivers use sample-and-hold to compare new information with old information to detect interference. 2) Most PCM systems, Polk's included, use the Hold feature to provide a failsafe set of positions for the servos. This is an advantage over pulse-width systems (our common AM and FM sets), which almost always go hard over toward the short-pulse end of the servo travel whenever interference occurs. That is what causes the AM/FM systems to generate a snap-roll-and-spin-down situation-something all of us are familiar with.
Radio Technique
I SAID in my February 1989 column that I would take a Lanier Seabird with me on my trip to Alaska. But it turned out to be too bulky, so I made a last-minute decision to take a Lanier Laser instead. The Laser stored neatly out of the way on the ceiling of the van, on bungees. (Bungees are long, cloth-covered rubberbands, about 5/16 in. in diameter and fitted with hooks on the ends.) I'm back in New York again, after a wonderful summer in Alaska. One of the smarter things I did in preparing for this trip was to remove the screws holding the interior moldings on the van's windows, one at a time, and slip on a swivel hanger meant for hanging pictures before putting each screw back.
Radio Technique
Narrow-band systems available now: Airtronics, Inc. offers a new line of super narrow-band Gold label receivers for the U.S. and Canada. Airtronics is also the first manufacturer to submit independent laboratory test results to AMA HQ which demonstrate that both the new receiver and transmitter modules meet and/or exceed the AMA Guidelines for narrow band (1991 and later) performance. The best part is that these narrow-band receivers and matching transmitter modules are being made available to owners of existing wideband Airtronics equipment. (Isn't that what I predicted last year?)
Radio Technique
WHAT'S AHEAD? This is part two of the discussion I began last month: Bob Aberle, George Steiner, and I have seen, and tested in various ways, some DC (dual-conversion) Rx, including the new Airtronics receivers, Futaba 1024 PCM, Polk's Challenger 720, World's Expert, Ace, R/C's Model 91, and the old Kraft KPR-8FD. They show some interesting characteristics: 1) Adjacent-channel interference is insignificant to the new dual-conversion (DC) receivers. Gold-sticker transmitters at 20 kHz channel separation (the 1991 situation) have less effect on these new receivers than Silver-sticker transmitters at 40 kHz separation had on the old receivers (the 1983-1987 situation).
