Polk's Modelcraft Hobbies has gone one better with its Tracker II computer-driven transmitter, which accommodates more than 90 memory positions. A synthesizer lets you select any one of the 50 RC aircraft channels using the LCD screen so you don't have to remove a module and twist any dials. You can also enter the channel number for each model into the memory along with the proper deviation.

When you first turn on the Tracker, a built-in scanning receiver (right inside the transmitter) scans the operating channel before allowing it to go on the air. The Polk's Seeker companion receiver can listen for an FM signal and then set itself to that channel. With this concept you could switch channels every flight and never have to wait for an available channel.

The fact that these computer-driven transmitters can store control data for many models means that you will need many more receivers (one for each model) but only one transmitter. Generally, the RC manufacturers would like to sell you an entire system: transmitter, receiver, and servos. Through the years, many of these manufacturers have priced airborne packs (receiver and servos) at practically what it costs for a full system. 

More recently, companies have come out expressly with aftermarket receivers and servos that will work from almost any computer-driven transmitter. FMA Direct has a complete line of receivers and servos. It even has a micro-size dual-conversion receiver (the M5) that weighs 0.35 ounce! Using aftermarket microreceivers and microservos is commonplace today, especially with parking-lot and indoor RC flyers.

When mixing and matching computer transmitters, receivers, and servos, you will have to contend, to a degree, with connector polarity. Connectors used on receivers, switch harnesses, and servos now follow the same convention.

On three-pin servo connectors, one outside pin is battery negative, the center pin is battery positive, and the other outside pin is the signal. Plug it in one way, and the servo works. Reverse the connector (some have keys that prevent this possibility), and the servo does not work.

One thing is for sure: you cannot blow out that servo with this type of polarity convention. Years ago this was much more of a problem. The only connector that is still different is the charger plug on the JR transmitters; the center pin and outside connection are different on this plug than on all others in the RC hobby industry.