What radio to purchase?

[headviking]

New to quads. But would like to start off with a quality radio that I can grow with. Looking at the.
Spektrum - SPM6700
DX6 6 Channel System w/ AR610 Receiver
or
Spektrum - SPM7800
DX7s 7-Ch DSMX Radio System with AR8000 Receiver
Why the receiver? I thought the receiver was built into the quad!

What do the channels mean? Will I ever need more then 7 channels?

Now will these radio bind with any quad I purchase and when the time comes, if I build my own quad, what should I be looking for to work with my radio?

Sorry for the 101 questions.

 

[Mike]

If you're buying a ready to fly quad, it may come with a receiver, but probably not - unless it comes with a transmitter as well. Typically, you buy the receiver separately (especially with a kit) because it needs to be compatible with your transmitter. That sort of answers your last question there - any radio won't just work with any receiver. Most radios run on 2.4Ghz, but there are a number of different protocols that have been developed for the radios to talk to the receivers. There are various reasons for this, but one of the features that is continuously being developed my manufacturers has to do with fast channel hopping to avoid interference.

If you're just starting out, it's always best to buy the tx & rx as a set if possible. If not, make sure you do a lot of research to ensure your tx & rx are compatible. Typically, most RX's are going to be compatible with all of the flight control boards as long as they have enough channels. With quadcopters, you generally want at least four channels, but if you want any room for growth, 6 or more is better. If money's not an issue, go with the DX7s, but really the DX6 will likely last you a very long time. The only reason the 7 channel setup might be better is because more and more add-ons, flight control board features, etc. are becoming available and oftentimes, they require another channel to control. Also, Spektrum is pretty awesome. I had a DX6i for a long time and never had any problems. I've also had cheaper tx's that have ended up costing me more than a higher end tx just to get working optimally.

 

[Hugh Hemington]

A multi-rotor requires at least four channels to fly -- four discrete signal paths between transmitter and receiver/quad. More channels can be used to turn LEDs on and off, invoke "RTL" (return-to-landing-point), take a still picture, turn video recording on/off etc. The break point in price is usually 8 or 9 channels. A Turnigy 9XR with "module" and receiver is around $60. Ten channels and up is typically over $100 and rises sharply with features and quality.

If you're new to quads, just buy a RTF (ready-to-fly) with a 2.4GHz transmitter. You'll want to learn "head-in" flying on something durable and cheap. And it's always nice to have something sacrificial to hand to kids who want to play with your REAL quad.

If you're set on buying a better radio to start, consider the FrSky Taranis. Bruce Simpson (RCModelReviews) swears by them, and that's a pretty good recommendation. That and a BNF (bind and fly) or PNF (plug and fly) quad will get you started. Or just get a RTF quad you like the look of. It won't hurt to have a $20 transmitter around.