2.4 GHz systems operate differently than your current 72 Mhz PCM or FM systems.
In the "old" 72 Mhz world, you have a transmitter, you buy a receiver, stuff the proper frequency crystal in it, and voila, the receiver and transmitter work very well together (assuming you have selected PCM/PPM properly, and in some systems, have the correct "shift" receiver).
And any receiver on your frequency is more than happy to respond to your transmitter, provided it, too, is on the same channel. Thus, the need for frequency control flags, pins, cards, whatever, at organized flying sites.
In the 2.4 GHz world, each transmitter has a unique identification code that is transmitted as part of its job. In the computer world, it would be known as a Global Unique Identifier (GUID).
There are no preassigned "channels" in the 2.4 GHz world as there are in the 72 MHz world. There is simply a narrow band of frequencies that all 2.4 GHz systems use, whether it be a telephone, computer wireless access point or other consumer item.
Instead, the various 2.4 GHz RC systems have to share the same band of frequencies and operate with each other.
Each 2.4 GHz system receiver when sold does not "know" which transmitter it is supposed to listen to. Plug things in, turn them on, and unless the RX is "trained" it won't respond to any transmitter, because it doesn't know who its "master" is.
Each new receiver must be "trained" to "learn" the unique identifier code from the transmitter to which it will respond. A simple process is built into each system to allow you to "train" the RX to listen to a given transmitter. This is called binding.
In the JR/Spektrum world, the process to bind a new receiver to a specific transmitter is simple. A jumper plug is inserted into one specific plug located in the receiver (usually the battery port, as the battery port only needs to use two of the three available connector pins). That third "unused pin" is grounded using the special plug, and when the RX is turned on, instead of acting as a normal receiver, it goes into "bind" (or "learn" ) mode. The transmitter you will use has a button located on the back to put the TX into bind mode. With the RX in bind mode and waiting for a transmitter to be bound, you simply hold down the TX bind button while turning on the transmitter.
The TX is in bind mode, the RX is in bind mode. The receiver sees the signal from the transmitter and "learns" the unique identifier code from THAT transmitter. Once the RX learns and saves that ID code, the bind process is completed. Turn the RX and TX OFF, pull the bind plug from the RX, and you're finished. From now on, that receiver will ONLY respond to commands from that transmitter, and no others. It will reject signals from a transmitter whose unique ID code does not match what the RX was trained to learn during the bind procedure.
In the 2.4 GHz world, Futaba receivers will bind and work ONLY with Futaba transmitters. Hitec RX's only will bind and work with Hitec TX's. Airtronics RX's will only bind and work with Airtronics TX's.
JR and Spektrum are a bit of a different animal, as JR and Spektrum share the same 2.4 GHz technology and architecture, allowing these two systems to work together. You can bind a JR 2.4 TX with any Spektrum RX, and any Spektrum TX to any JR RX, as well as the usual JR to JR and Spektrum to Spektrum.
(There are some limitations, but those are limited to the first generation DSM technology pioneered by Spektrum).
Spektrum's incarnation of 2.4 GHz systems uses a technology they originally called "DSM". The second generation systems brought out "DSM2" technology.
Futaba calls theirs "FASST" and utilizes the same 2.4 GHz band in a way different from that of the way JR/Spektrum do.
Airtronics and Hitec call their incarnation something different.
Bind "n" Fly. Horizon (the JR/Spektrum distributor) has come up with the idea that people may already own a JR or Spektrum transmitter and may want to buy one of their ARFs, ready to fly, and don't need another transmitter (or don't want to pay for an extra transmitter).
They have included compatible "DSM2" technology receivers in their products that will also bind and operate with a JR or Spektrum transmitter. So you can save $20 or $30 on the ARF if you already own a DSM2 transmitter, and simply bind the ARF to your radio. If you DON'T have a DSM2 compatible TX, for that extra $20 or $30, they throw in a cheap, but functional transmitter. It's a nice marketing strategy to spread the DSM2 technology. Once bound, that new ARF will listen only to YOUR TX, no one elses.
Mode I and II (and III and IV and...) have been around a long time, going back to the basic 27 MHz AM systems of long ago.
It refers to which primary controls are found on each stick.
Mode II -- Throttle is on the left stick (vertical), Rudder is on the left stick (horizontal), Elevator is on the right stick (vertical), and Aileron is on the right stick (horizontal).
Mode I -- interchanges the throttle and elevator positions. Airplane pattern flyers often found it easier to control their planes in precision pattern maneuvers if they separated the aileron and elevator functions by putting one on each stick.
Some of the other modes are a bit more obscure. Mode II is prevalent in the US.
Model Match is an additional feature found in the JR/Spektrum DSM2 radios. You can store up to 30 different model setups in an X9303. The transmitter has only ONE unique ID code that is shared amongst those 30 possible models. Without model match, you could bind any number of receivers to your transmitter, they would ALL respond to THAT transmitter, regardless of which model you have selected. This is the same as your PCM system -- any RX on your channel will receive and work with your TX.
Model Match adds one piece of information for the RX to "learn" during bind mode. In addition to the transmitter's unique identifier code, it also learns which of the 30 model memory setups you are using. This means that you can have 30 different models programmed into your transmitter, but only one of 30 matching receivers will respond to a specific model setup. This prevents you from having your transmitter set to control your monster 1/4 scale airplane and picking up your 90 3D heli instead. Turn things on, and the heli RX won't respond to that plank setup, because the model number doesn't match.
It saves you the embarrassment (and cost) of grabbing your TX and heli, and taking off with the wrong model selected...something that can easily happen with your XP9303 PCM rig.
Yes, Spektrum makes a module system that simply plugs into your X9303 and turns it into a 2.4 GHz system. (This module pretty much plugs into ANY JR transmitter that has the plug-in RF module, and that has been around since way back in the early days with the Century VII transmitters. It's NOT specifically for the X9303).
The module replaces the RF module plugged into the back of your 9303 (or other JR TX), and the antenna, with its own transmitter module and antenna. No permanent changes are made to the TX, you can switch back and forth between your old PCM stuff, and the new 2.4 GHz stuff.
With this "module" system, you DON'T GET the MODEL MATCH feature. That is reserved for "native mode" (purpose-built 2.4 GHz system such as the X9303).
Spektrum also makes a module to convert Futaba PCM/FM radios into JR/Spektrum compatible 2.4 GHz systems. Again, the standard RF module is replaced in the TX, along with the antenna. This allows a Futaba flyer to continue to use his existing 72 MHz stuff and use Spektrum 2.4 GHz stuff. Again, no Model Match feature in the module systems.
As for that $629 system -- do yourself a favor and shop for a system that has ONLY the TX and RX if you intend to switch over. These usually include the wall-wart charger and an RX battery pack, but no servos. The stock servos (DS821) are not that good. Keep and use the servos you already have, or spend the money you save on decent servos of your choice.
Pretty much any current analog or digital servo on the market is fully operational with the new 2.4 GHz systems, sharing the same plugs and wiring order.
You CAN simply add the module to your existing XP9303, but as noted above, you don't get the model match feature.
If you insist on the Model Match feature, you'll need to pick up a JR or Spektrum system. The X9303 is a fine radio (since you have an XP9303, you're already familiar with 99% of the programming). The Spektrum DX-7 is also a fine radio, not quite as many frills as the X9303, but it's no slouch by any stretch of the imagination. And it does have the Model Match feature.
The 2.4 GHz systems do away with the need for frequency pins, cards, flags, and other "control systems". You can't shoot someone else down, they can't get to you, either. Nice.
Hope this clears up things for you.
* Making the World Better -- One Helicopter at a time! *