Jim, I'd like to add some fairly non-specific transmitter info to this thread that may help people make a decision on purchases. There are some examples throughout of references to Spektrum, but it's more to show a point about features, or bind n' fly. Hopefully this helps anyone looking to buy a transmitter, REGARDLESS of the brand!
Aircraft - This breaks down to a couple of things - What types of planes are you looking to fly? Very simple gliders, warbirds that have retractable landing gear and bomb drop capabilities, racing quadcopters, helicopters, etc? The different aircraft you fly may require more channels to operate some of the features, and so you may need more channels. Let me give an example of how the channels break down: on most basic planes, you have 3 channels - Ailerons, elevator, and throttle. Sometimes, that gets changed out to Elevator, rudder, and throttle, but the principles are the same - one channel for turning left/right, one for up and down, and one for the gas.
That said, more and more planes are 4 channel, where you see Ailerons, elevator, rudder, and throttle, which help make the plane more responsive. Add in flaps to a plane to help slow it down in landing? Now you're up to 5 channels. Retractable landing gear? That requires another channel. At minimum, if you're buying a radio, you want at least a 6 channel radio, but if you plan to grow into some of these more advanced planes, an 8 channel is recommended.
Brands - There are quite a few out there: Spektrum, FrSky, Futaba, FlySky, to name a few - they're all different, and I equate this to a "Android vs. Apple, Chevy vs. Ford/Mercedes vs. BMW" debate. While the transmitters do the same basic functions, they use different protocols, and aren't necessarily compatible with another brand. Some of the radio systems have modules that you can buy to add on additional protocols, but not all of them - and some of those modules may require opening up your transmitter to make modifications internally, which may likely void your warranty. If you've just dropped $300-$500 on a transmitter, I can definitely understand being a little leery of tearing it open.
Also, many of the "bind n' fly" planes that are out there are protocol specific - for example, if you purchase a Horizon Hobby plane like the Timber, or Apprentice, you'll find that they come with a Spektrum receiver in it. Now, this doesn't mean that you can't fly it if you have a different protocol radio, but you'll need an aforementioned module (if your radio supports it), or spend extra money buying a receiver to replace the Spektrum receiver. Some people don't have a problem with this, but if you want to fly a lot of the Bind n' Fly planes, it may be a consideration to pick a transmitter that will be compatible from the start.
Programmable - This is basically an LED screen that allows you to go in and set up the plane for your type of flight (but it may also be programmable through a cell phone/tablet or computer connection). For example, if you're flying a plane that the servos are backwards on (i.e., you push a stick left and the plane goes right) you can switch the servos around so it goes in the correct direction without having to do some disassembly and turn the servo around. It'll also allow you to do some micro trimming, so you can get the ailerons/elevator/rudder centered properly in case you had a little slop in building your plane. And, there's settings for different flight modes that you can program in - say you want to set up some settings for a particular plane that are a bit more limited, so that it'll fly with less reaction when your kids fly, vs. being able to do some crazy aerobatic flips, rolls, and turns, all at the flip of a switch. That's where programmability comes in, and it's a HUGE bonus. Lots of radios offer this, but the cheapest ones don't have it, or use switches to accomplish this functionality and it's all a combination of "flip this switch with these three others off in order for it to take effect." Also, some of the radios use OpenTX, which have a steep learning curve for programming, and it's almost a programming language in and of itself. That said, it DOES offer quite a bit of functionality, but if you don't have anyone that can help you (a good portion of the manuals for programming are written in Programmer language, then translated to Chinese, then from Chinese to English by someone who learned English as a Second Language, so a lot of the translations are difficult to understand), OpenTX can be a bit of a bear to muddle through.
Model Storage - working hand in hand with a programmable transmitter, model storage allows you to have multiple models stored in a transmitter. A lot of people initially think, "I only need it for one model." Others think, "Ok, maybe 5." Let me tell you that if you are going to build Flite Test planes, you want a radio that can do at least 10, preferably more. I have 13 models in my radio at the moment, which include my Flite Test builds, my computer for simulator time, and 3 different quadcopters. Cost is a factor in this one; cheaper radios have smaller limitations on how many models you can store.
Assistance/Support - Are you part of a club/flying field? Do you have friends who fly? If so, what are the most common radios being used in the area? Sure, this may sound like a "jump on the bandwagon" speech, but there are reasons for it. If everyone else at your field is using a particular brand of radio, it generally means two things - the radio is of good quality, and that they can help you if you need help tweaking a setting. Hand them a radio that nobody's seen before, and ask them for help, and they might be able to muddle through it, but it might be a bear at best for them. Also, if you are learning to fly with someone else via buddy boxing (they set up a radio as a master control for the plane you're flying, and your radio is slaved to theirs, so they can take over if things get out of hand), having a radio that is of the same brand makes it a LOT easier to do master/slave buddy boxing.
Features - There are a LOT of features that you'll pay extra for. Some of them are worth it, some are not. Let me give a great example, with the Spektrum radios. Spektrum has a Dx6e and a DX6 model. Both are 6 channel programmable radios. However, the Dx6e does not offer Diversity antennas, and the DX6 does (diversity means there are two antennas broadcasting signal at the same time, at different angles; the plane picks up whichever is the strongest signal and uses that one, in theory preventing loss of signal). In addition, the DX6 offers voice alerts, while the DX6e does not; these alerts will have a voice call out things like, "30 seconds remaining", as opposed to a beep or a tone for the same alert. Are these necessary features to spend the extra money on? I personally think that they are, but that's entirely up to you.
Transmitters are something that you're going to use for a number of years, with a variety of planes. This, and a battery charger (which is a whole other can of worms), are the two big investments you should make in this hobby. Ultimately, you're going to buy what you want, and what should best suit you, and that's what SHOULD happen. But I wouldn't recommend buying the cheapest radio out there, either. Spending $60 now, and then say, $250 later for the radio that you really want/need? Me personally, I'd rather invest in the $250 for something that'll last me 10-20 years before I have to go buy something that replaces my "old" technology.
