2.4GHz RC system compatbility

Your Reviewer

My Credentials
So who's doing this reviewing then?

Well I've been building and flying or driving radio controlled models for over 40 years and during that time I like to think I've built up a reasonable amount of knowledge.

I'm also a qualified electronics engineer who has worked in radio frequency, analog, digital systems and software for more than three decades. In fact I designed and built my first RC set back in 1969.

For the past nine years I've also been involved in the design and manufacture of some rather sophisticated engine technology and UAV flight control systems.

So, chances are I've been there, done that and have a huge pile of tee shirts to prove it.

Right now I'm heavily into 3D flying and enjoy all aspects of the RC hobby. I may be old but I don't feel it.

In the Pipeline

Here's just a little bit of what's to come on this site...

RC explained: Demystifying terms such as PCM, PPM dual conversion, single conversion, full-range etc., this feature will explain it all.

Cheap Chinese Engines: Just how good are those cheap Chinese glow and gas engines that sell for half the price of their "brand-name" equivalent? I put several to the test.

Build your own radio gear?: Back in the old days, building your own RC gear was not uncommon and now the arrival of 2.4GHz has made it practical again.

How compatible are 2.4GHz RC systems?

WHY ARE WE LOCKED-IN TO A BRAND?

Dated: 23 Mar 2010

Back in the days of FM radios operating on much lower frequencies such as 35 or 72MHz it was pretty easy to find a compatible receiver that would work with your brand-name transmitter.

Although there was a rift between Futaba and JR on the 72MHz band (different shift), on all the other bands there was almost a 100% compatibility between brands of radio equipment when FM receivers were used.

Oh how that has changed in the world of 2.4GHz.

One of the most oft-asked questions I hear is "Will this (cheaper) receiver work with my (expensive brand-name) transmitter?"

Invariably, the answer is no.

If you have a Spektrum/JR DSM(2) radio then you're stuck with using a Spektrum/JR receiver.

If you have a Futaba FASST radio then you're stuck with paying through the nose for their very expensive FASST receivers.

None of those attractively-priced Chinese brands will work.

Neither Corona, nor Assan, nor FlyDream, nor FlySky, nor FrSky, nor any other receiver will bind with your expensive brand-name radio unless it has a matching transmitter module installed.

What's more, brand-name manufacturers are keen to preserve this this state of affairs. They know that, once you've bought their radio, you're going to have to come back and pay whatever they ask when you need more receivers.

Whereas, in the days of FM radios on the MHz bands, you could rush out and buy a cheap but cheerful Corona FM receiver for a third the price of a genuine Futaba or JR unit, today you're stuck with buying "the real thing" and often that means handing over very sizable sums of money.

This situation is even worse when you realize that a few of the Chinese-branded receivers these days are actually better than some offerings by the big-name brands which cost three or four times as much.

So why aren't the Chinese making compatible receivers that can be used with JR/Spektrum and Futaba?

Well the use of spread-spectrum technology makes that task a whole lot more difficult than was the case with FM. All the brand-name manufacturers used a common standard for their FM transmitters. This standard was well documented and easy to implement.

By comparison, 2.4GHz spread-spectrum is a whole lot harder.

Reverse-engineering a spread-spectrum signal can be a difficult (but not impossible) process that requires considerable knowledge, skill and the right equipment. All of that represents a significant investment, something often not available to the kind of small manufacturers that are currently building RC their own systems in China.

What's more, Futaba (for instance) is using their own custom-made chips which means that even if/when the Futaba spread-spectrum system is reverse engineered, it's probably not going to be a case of simply throwing together a compatible receiver from "off the shelf" components.

Finally, there's the legal perspective.

There can be little doubt that if/when Chinese manufacturers start spewing out brand-name compatible 2.4GHz receivers at a fraction the price of the real thing, lawyers will be unleashed and (in the USA at least) the Digital Millennium Copyright Act (DMCA) will be scrutinized to see if there's any way the importation and use of such receivers can be banned or prosecuted.

Remember that the shift to 2.4GHz and the resultant ability to lock customers into your product is a gold-mine for RC manufacturers. That's not something they're going to give up without a fight. Let's face it, the only reason that Futaba (for instance) can demand three or four times the price you'd expect to pay for a Chinese-made receiver is because they have no competition -- only their receivers work with their radios.

If/when competition appears, and you can buy a good, reliable 8-channel FASST-compatible receiver for $35 instead of $140, Futaba will lose the ability to demand such high prices for its products.

In the meantime, if you're planning on buying a new native (non-modular) 2.4GHz system then be sure and factor in the price of extra receivers. It can make a huge difference to the total cost over time.

But here's a question for you...

If you could buy a proven-reliable "compatible" receiver for your JR/Spektrum, Futaba, Airtronics or other brand-name radio, would you? Or would you remain brand-loyal, even although it meant paying two, three or even four times as much?

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