A little bit of information to clarify "binding" of 2.4 GHz receivers.
With the "old" 72 MHz stuff, you really only needed to make sure that the receiver you were about to use was on the same frequency (channel) as the transmitter. (Yes you may have had to think about positive shift, negative shift and a few other odds and ends, but once you had the right receiver crystal plugged in, the receiver would function with your transmitter -- And just about everyone else's transmitter on that same frequency). Remember having the frequency control board at your flying site -- and you didn't turn on your TX unless you had the pin that matched your TX frequency? We always had to beware of accidental "shoot downs".
The 72 MHz band was chopped up into 50 channels, numbered 11 through 60. Each channel was centered around a specific slice of the RF spectrum, occupied a certain width of the spectrum, and with a small guard band in-between to insure that channel 11 didn't splatter all over channel 12....and so on.
That particular slice of the 72 MHz spectrum was set aside by the FCC for industrial controls use, and RC use, and we shared that slice.
The 2.4 GHz systems operate in a completely different fashion. All 2.4 GHz systems operate within a slice of the RF spectrum a little further up the frequency range, centered around the 2.4 GHz value. But that 2.4 GHz splotch of RF is also shared with just about every other modern day appliance operating in the 2.4 GHz band. There are no "channels" per se, set aside for each transmitter, there is one slice shared by all. You're flying with cell phones, cordless phones, WiFi, wireless internet, and all sorts of other consumer goods.
How does your lonely little receiver know WHAT to listen to? Think about your PC. It's connected to the internet with zillions of other devices. How does anything on the internet know how to communicate with only your PC when everyone else in the world is hooked up to the same network?
Inside your PC's Ethernet interface is a device with an address that is unique to that bit of hardware. No other bit of hardware shares that same unique address. It's referred to as the MAC address -- "Media Access Control Address". That address is used by stuff out on the internet to transfer information to and from your PC, and your PC only. Through the magic of software and hardware, that unique MAC address gets translated to your IP (internet protocol) address.
With all the traffic on the net, only stuff sent to your unique MAC address makes it all the way through to your computer. And stuff from your computer to the world also contains that MAC address so others know where it came from.
Back to the 2.4 GHz world.
Each 2.4 GHz transmitter has built into it something known as the Global Unique Identifier (GUID). It's a number unique to each transmitter. This GUID is used by the receiver to identify transmissions meant only for it, and no-one else. When you buy a new system, or add a new receiver, the receiver needs to be "taught" to listen to only your transmitter. Hence, the "binding" process. In a Spektrum or JR system, one plugs a "binding plug" into a special port on the receiver (usually the traditional battery socket. The plug connects what would be the "unused" pin of the battery port to ground. When power is applied to the receiver with the binding plug installed, the receiver software goes into a "learning" mode. Meanwhile, the TX has a pushbutton (or other switch) that is depressed WHILE turning the TX on. This puts the TX into the "learn" mode, as well. With the TX in close proximity to the RX, and since both are in "learn" mode, the receiver listens for the GUID being sent out by the TX. At the end of the "learn" or "binding" process, you have trained the receiver to listen only to signals from your transmitter. Turn things off, remove the bind plug, you're ready to roll.
Binding need only happen once, it's not a "do every time" thing. You can re-bind any time you wish, that's usually reserved for when you move equipment from aircraft to aircraft, or change receivers or other special purposes.
Your transmitter ships out informational packets of stick position information, each one has the TX GUID included, such that your receiver can identify which batch of data out in the ether is assigned to it. The receiver will ignore all other transmissions whose GUID don't match what it learned at binding time.
There is some other magic going on between your TX and RX, but essentially, once the receiver has been trained to your transmitter, it should respond only to messages from that transmitter.
In the case of JR and Spektrum systems, other vital information learned by the receiver at binding time is which model setup your transmitter is set to at the time it's bound. My JR X9303 can store setups for 30 different models. The newer X9503 can store setups for 50 different models. This additional information is used for what the Spektrum/JR people call "Model Match".
The newer 72 MHz systems that had been sold were already capable of storing setups for multiple models, but with each different model, you needed to be very careful about selecting the correct model setup in the TX that matched the heli or plane you were about to fly. If you happened to have the wrong model selected, the RX didn't care, responded to the transmitter and you could end up with your hands quite full at takeoff time.
With the model match feature, even after you have properly bound the RX to the TX, the RX will still recognize your transmitter's signal, but it won't respond to the transmitter unless the model memory that's active in the transmitter matches what the receiver learned at binding time. It's a bit of extra insurance to make sure you don't try to fly with the wrong model selected. Not all 2.4 GHz systems HAVE this feature. It's in ALL JR and Spektrum systems, something similar is present in the high-end Airtronics systems, and the others, I don't know off-hand.
Using the GUID coupled with some other cool network-inspired ideas, you no longer need the frequency clip before you turn your TX on, and you should be able to fly glitch free, even in spite of competing interference.
Some of the other cool by-products of the 2.4 GHz technology is a great deal of immunity to metal-to-metal induced RF noise, immunity to the RF noise given off by spark-ignition systems, and other stuff that the 72 MHz flyers needed to worry about.
Your 72 MHz stuff would be just fine, but with an electric heli, you do need to worry some about noise from the electronic speed control coupling into your RX and wreaking havoc. Some simple precautions are usually needed to insure trouble-free performance, but by no means is your 72 MHz stuff outdated and obsolete. Just make sure your batteries are fresh after all those years of sitting around gathering dust.
What heli you buy is completely up to you. Whether a kit, ARF, or something in-between, make sure it's properly assembled and that loctite was used where it needs to be.
Good electrics? There are tons of them, from very small stuff such as the E-Flite Blade MCPx, Trex 250s, 450's, 500, 550, 600, 700 and larger. Check out the stuff sold by the advertisers here on RR, it's all mainstream, and for the most part you can't go wrong with any of the main-stream stuff. Align, Rave, Miniature Aircraft, Synergy, Velocity, Outrage, Gaui...it's a cool world these days, there are so many good choices, it's hard to just pick and fly one.
Welcome back, learn the new electric heli and radio lingo, do your homework and enjoy.
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