Radio Technique
THE QUESTION: What low-priced radio should I buy for 1988? I toured some of the major RC systems suppliers, asking them that question. Before I give you their answers, let's review what we already know. 1) Use of the frequencies 72.08, 72.16, 72.24, 72.32, 72.40, 72.96, and 75.64 MHz for control of model aircraft became illegal by federal regulation, effective December 20, 1987. Those frequencies were "shared" with other high-powered services that interfered with model aviation so much as to make them useless in some parts of the country. The FCC gave us five years to get our existing equipment converted to RC38 through RC56 (which are exclusively for model
Radio Technique
SOME interesting new products have come my way. In 1983, the AMA Frequency Committee took a lot of flak from manufacturers, because we didn't define new RC channel flags early enough for the manufacturers to bring their new flags to market with new RC systems. Consequently, some early transmitters on RC38-RC56 were sold with either "illegal" flags or no flags at all. When "legal" designs reached the market, they generated the following complaints: 1) Some required you to store the transmitter with the thinnest part of the antenna extended to support the frequency flag, which caused damage. 2) Some put a lot of weight out at the tip of the antenna, where it unbalanced the transmitter. 3) The flag drag tried to pull the transmitter out of your hands when flying in a wind, as in Slope Soaring.
Radio Technique
Latest news from the 1988 RC frequency-utilization scene: A joint effort of the Radio Control Manufacturers Association (R/CMA) and the AMA is the certification of transmitters-new or frequency-changed. Sorry we can't show you these seals in color, but the upper one is gold, and the lower one is silver. A transmitter bearing a gold seal is certified narrow-band and can be used in AMA-sanctioned competition on the 12 "lower-band" channels (RC12-34). A transmitter bearing a silver seal is certified wideband and can be used in AMA-sanctioned competition only on the 10 "high-band" channels (RC38-56). There's quite a bit more information in this month's column.
Radio Technique
OLD FRIEND REVISITED. I first reported on the Accu-Tach 2 in the February, 1985 issue of Model Aviation. It is an instrument which combines a digital voltmeter, ammeter, and tachometer in one light and handy package. My Accu-Tach 2 has provided excellent service for three years and is an essential part of my field kit. The manufacturer of this device is now the Norcal Avionics Div. of A-B Tech Inc., 5689 Glasgow, Troy, MI 48098; telephone (313) 828-8210. Accu-Tach 2A adds a remote tachometer probe, clip leads, and a handy zipper pouch to the catalog. A couple of labels have been added to define the function of the Tachometer/Voltmeter selector switch and of the built-in tachometer sensor; otherwise, the the Accu-Tach remains its old, dependable self.
Radio Technique
RC SYSTEM TESTING-the modified Myers/Aberle test procedure. Bob Aberle and I have modified our test procedure (which was originally published in my January 1986 column) slightly to match the 1988 situation. Our new test matrix is shown in Figure 4. The basic change has been transmitter is at least -50 dB at F0 ±20 kHz. OWBAM transmitters: We use George Steiner-modified Kraft synthesizer modules. These produce AM signals with sidebands of about -35 dB at F0 ±20 kHz with 500 Hz frequency accuracy. Unfortunately, they radiate slightly less power than do the NBFM synthesizers.
