Radio Technique
HAPPY NEW YEAR! During the 10 years I've been writing "RT," we have tested many radio systems. It has been a rare thing to encounter a defective or unusually-poor-performing system, regardless of price. In fact, some of the least expensive sets really have shown the best performances. Likewise, some of the highest-priced sets have produced the worst performances. The overall spread between best and worst has been small, once you discount the two or three real stinkers that we all know about (now). Reasoning that our previous test method may not have been showing us the most important differences, we retested a representative group of RC systems in an attempt to find a better test method. Table 1 shows the combinations of receivers and transmitters tested.
Radio Technique
MORE on Third-Order Intermodulation (3IM) avoidance. I have just received a very nice letter from Eldon Wilson, AMA 5247, of San Angelo, TX. I will share parts of it with you now. Mr. Wilson writes: ". . . you may wonder if your messages are ever considered. Let me relate how your `group frequency control' (July '85) worked. ". . . Our recent West Texas Fun Fly saw 93 transmitters impounded, of which 31 were on the old frequencies. On the new frequencies were 29 AM and 33 FM transmitters. In two days of flying, with four to six airplanes up at a time (75.640 is still being used), we logged 194 flights without a single case of interference or unexplained crash. Being one of the originals in RC (since 1950), I consider this a record.
Radio Technique
WHAT'S HAPPENING with those RC frequencies? This month, I have received several letters asking about AMA changes in the RC channel assignments for 1986. There aren't any! All of the channels you have been using, you will continue to use in 1986 and 1987; and all forms of modulation (AM, FM, PCM, etc.) are, and will continue to be, legal and proper. They will continue to be legal and proper through 1991 and beyond, so far as anyone knows today. In 1988 (that's two years away), we will be obliged, by the FCC, to abandon the old even-frequency channels (72.08, 72.16, 72.24, 72.32, 72.40, 72.96 and 75.64 MHz). Therefore, you should have converted your old transmitters and receivers off those old RC channels and onto one of the new ones before January 1, 1988. We've been urging you to do that since January of 1983.
Radio Technique
MORE ABOUT the safety question . . . A while back, I commented on the way that our models are getting bigger and faster, without visible evidence of any stress analysis having been done or pre-flight static strength-testing. I asked whether you, my readers, agreed that Model Aviation should present articles on those subjects. So far, I have received four well-written letters emphatically in favor of the idea, and none opposed. Now, let me tell you a true story: Some time ago, I undertook to build a Sailplane as a review for a magazine (not MA). The wing had plug-in tip panels, each supported by a 1/4-in.-dia. dowel at the dihedral joint. I looked at the plan and said, "Too weak." On the assumption that no competent designer would put money into creating a kit while leaving in such an obvious weakness, I decided to perform some elementary stress analysis.
Radio Technique
PROPER TUNING is important! 1986 has already been a strange year. I took a long Christmas vacation for the first time in my life and since returning have been literally buried in work at Grumman. Meanwhile, at the same time, reader letters have come in a flood. Reader letters are usually broadly divided into three categories: 1) "Which RC radio shall I buy?"; 2) "What's the new RC channel setup?"; 3) "(Where can I get information on) (Who fixes) a particular old radio?" Since publication of the January '86 issue, I have also received: 4) A large number of letters on 3IM (third-order intermodulation interference).
