Focus on Competition
Greg Hahn
Radio Interference
Questions often come in groups and lately I've fielded several calls asking about possible radio interference from different types of towers and manufacturing facilities. I can understand the worry and getting a straight answer from anyone can be frustrating. I have often found that not getting a good answer is not because someone is hiding something, but the fact that few people really know what or how to answer the questions. This is especially the case with 2.4 GHz radios where pinpointing a potential problem is difficult because we're not working with specific frequencies.
I spoke the other day with Mel Ziska from District VI about how when a club seems to have a problem, coming up with an answer is not an easy task.
Back in the day, any trucker with a good CB radio running a linear could end our flying day in a hurry. Thank goodness that was only a fad, and now we're on to bigger and better things such as cellphones and Wi‑Fi.
To keep this as simple as possible (I'm not an electronics engineer either), most of the outside interference we deal with today on our "old" 72 MHz sets has to do with shadowing or the effects of power output. The interferer is not actually operating on one of our direct frequencies but is transmitting on an adjacent frequency with enough power output to cause a problem (big footprint).
This issue typically doesn't come from towers but from manufacturing facilities using radio control for their overhead cranes and other automated systems. Hospitals can also be a problem sometimes, as we saw recently with a club in Minnesota.
Most of the problems with 72 MHz come from within our own equipment or the airframe it's operating in. Any metal-to-metal contact, when combined with vibration, will often create the frequencies that interfere with our receivers and the filtering process is not strong enough to cancel it out. Problems such as bad engine bearings, metal clevises, loose motor mounts, and nuts and bolts in general can and will cause problems to the point of causing a crash.
I know many of you had a feeling that now that you're on 2.4 GHz you'll never crash again ... Well, not so fast. In addition to the venerable dumb thumb (what's that?), we still live in an era where the air is a very busy place. Our use of the 2.4 GHz band has given us some great perks such as no frequency pins, no need for impound, and better resolution, but the air is still busy and that radio traffic does have an effect and can cause problems.
Think of all of the other gadgets and widgets that have been invented in roughly the past 10 years that also operate on 2.4 GHz. All of these new things add to the radio traffic, making the link between you and your beloved model more difficult to hang onto. Granted, our receivers and equipment have become so good that they are nearly bulletproof, but they're not perfect.
The point of all this is to make you aware of what is out there, that problems still exist, and that most of it is a traffic issue. Rarely does one thing such as a cell tower or one building cause a problem. It's usually a group of things all working together to cause you grief.
Be safe and have fun. Greg Hahn
Transcribed from original scans by AI. Minor OCR errors may remain.
