Making the Radio Control work properly is one of the areas that gives starting Roboteers the biggest amount of trouble.
Remember, you only ever see video/TV of the matches where the robots perform well. The amount of times they sit there and twitch refusing to move, or only mopve intermittently is far more common that you would think. This baffles beginners, since they cant understand howcome a radio that can make a RC car run at 500 feet distant cant keep their robot running when its only 5 feet away
Due to the nature of our machines, with large powerful motors, running at much higher currents than standard RC cars or planes, generating massive amount of electrical noise, plus the need to have a small well protected antenna behind metal armour panels (If you poke a big antenna out of your robot, it is guaranteed to get chopped or broken off sooner or later), they require radio systems far better in quality than your little Toy RC cars do.
Do *not* buy an old 2nd hand 29mhz or 36mhz FM Radio system of ebay for $50 and expect it to work for Robot Combat. You *will* get your butt kicked and quite likely suffer far more damage in repairs than buying the more expensive radio would have cost you.
At present, the standard RC radios that have been *proven* to give the least trouble are the top-end PCM Futaba's.
The models are the 7CAP and the 9CAP with the R138DP PCM Receivers.
Expect to pay at least $400-$500 for one of these setups from Tower Hobbies (www.towerhobbies.com).
What ?! $500 ?!? Well, yes, unfortunately, this is not a cheap sport if you want to play with the experienced competitors. These radios will "just work" and if looked after, will last you 5 or 10 years and operate cars, planes, boats, helicopters and anything else you might want to play with in the future, so look at them as a long-term investment in radio control hobbies.
They are quite complex to program as well, with many multiple-level menu's and a *lot* of features. If this sort of thing confuses you and you dont have the patience to explore the menus and programming, ask an experienced builder who will usually be happy to program it for you.
A new radio on the scene that is looking quite promising so far is the "Spectrum" radio - http://www.robotmarketplace.com/marketplace_rc_radioDX6.html∞
These use a new spread-spectrum transmission technique with digital error-correction in their transmission making them *very* immune to noise. They also operate at a much higher frequency (2400mhz instead of 29 - 75 mhz) which means their antennas can be much shorter and still receive a good signal.
They do not require crystals, since they automatically find and lock onto a free frequency without the user having to do anything, so you dont need to worry about checking to make sure that noone else is using the same frequency you are, which is a big bonus.
If you are considering one for Robot Combat use, make sure you get the model with the *B*R-6000 receiver, and NOT the *A*R-6000 receiver. The "B" model is specifically designed for use with "Bots". The "A" model receivers only failsafe on one of the receiver channels when they lose the signal, and leave the other channels where they were last set, which is dangerous and illegal for robot combat use, where your robot is required to completely stop (on all channels, weapon and drive) if the signal is lost.
They still arent cheap at $300-$400 for a 6 channel stick unit, but there are no cheap solutions that are guarranteed to work in Robot Combat applications.
Some *Skilled* radio/electronic builders have managed to get by with cheaper radios, through careful design and placement of antenna's, lots of work to supress the noise radiated by the motors and wiring, and *extensive* testing and fine tuning of their robots well before the event. Even then, they sometimes suffer radio problems at a bad time, as the radio noise inside the arena (aurrounded by lights, computers, other robots, metal frames and so on) is quite often worse than your kitchen floor at home, and what worked well there, will quite often fail in combat.
If you can possibly afford it, do yourself a favour, get a *good* radio, and save yourself a lot of heartache as your carefully built killing machine sits dead in the arena, deaf to your demmands to move, while your opponent dances around you taking you to pieces. If you just cant afford that kind of dollars, then make *sure* you get your robot finished *well before* you want to compete (yeah, right) and allow for plenty of testing and fiddling time to get the cheaper radios dialled in and working. You will regret it if you dont.
If you would like more *technical* detail on how radios work, this is an excellent page to read