Spread Spectrum is Spread Spectrum
As I mentioned in a previous column, from time to time I’ll be addressing questions that are either about new technologies or may seem confusing. Through emails and phone calls, I can get an idea of what issues our members are most concerned about. I’ll take this month to put a few of them out there.
I have fielded several questions about using spread spectrum for surface and air at the same time. It’s different from what we’ve been accustomed to since the beginning of RC: there is now no difference in radio frequency between air radios and surface radios.
Spread spectrum is spread spectrum; there is no distinction between the different categories anymore. It doesn’t matter whether you’re flying an airplane or running a boat or car — they all work together now without interference. Today, the only difference in radios is the power output between surface and air units.
Normally, a surface radio will have a lower power output, which translates directly into shorter range. This is no problem when you run a car or boat with airplane equipment, but if you fly with surface equipment you may encounter range problems, so keep this in mind if you’re mixing systems.
Servo compatibility
One more thing to consider if you’re using the new spread spectrum equipment is servo compatibility. The servo itself will be no problem, but it has been recommended for some time now to use six-volt (five-cell) battery packs with spread spectrum receivers because of their higher cutoff voltage. Several servos still in use will not tolerate continuous six-volt power and will eventually fail. Check the performance data on the servo before you install it.
How many spread spectrum radios can be on at once?
Another often-asked question is how many spread spectrum radios can be turned on at the same time and still be safe. The jury is still out on that one. Your best bet is to follow the manufacturer’s recommendations.
There has been some testing. An article written in 2008 by Cal Orr explained in detail the testing he did where, if memory serves me, he had more than 100 spread-spectrum radios (by various manufacturers) all on at the same time while flying, with no apparent interference.
Also, there was an attempt to set a record at the Southeast Electric Fun-Fly meet for the most RC airplanes in the air at one time. I can’t recall the exact number, but it was an astounding amount of radios to be on at the same time; 150 to 175 comes to mind. I’m sure testing will continue and I’m hoping we arrive at a number we can all live with. It’s still better than dealing with frequency pins.
AMA recommendations
On a side note, I’m often asked what the AMA recommends regarding requiring pins for spread spectrum radios and whether impound is required. Of course, what a club does is up to the club, but we recommend:
- Continuing with an impound for the 72 MHz fliers.
- Having pins available for the spread spectrum fliers.
Many still fly on both systems, and you don’t want to get caught turning on your 72 MHz radio without a pin. Consider using a pin until spread spectrum becomes universal.
Transcribed from original scans by AI. Minor OCR errors may remain.
