Radio Reception Problems

From Combat Robot

Combat robots are electrically very 'noisy'. Electronic speed controllers, relays, and motors all contribute to electrical noise in the radio frequencies that makes reception of the control signal from your transmitter difficult. The problem is particularly acute in larger robots with higher-power components operating in large arenas.

Steps you can take to avoid/cure reception problems:

• Avoid AM radios – Inexpensive Amplitude Modulation (AM) radios are allowed in many events for robots up to 12 pounds without active weapons, but they are particularly sensitive to interference from robot components. Use a coded Frequency Modulation (FM) or digital 900 MHz or 2.4 GHz system for best reception.

• Expose the antenna – Plastic armor is transparent to radio waves, but metal or carbon armor blocks reception. Get your antenna out of the box! The antenna should ideally be stretched out vertically, but smaller 'bots are going to have a problem flying a 3 foot antenna mast. You can get good reception using a base-loaded Deans Mini Antenna that is only a few inches long. Insect class bots in small arenas can wind most of the antenna wire around a plastic drinking straw with just the last few inches exposed.

• Keep antenna away from metal – Put some space between your antenna and your armor. Don’t lay the antenna flat against a metal/carbon plate.

• Put suppression capacitors across motor brushes – Motor brushes are noisy! A ceramic capacitor (0.1uF) across the positive and negative motor leads as close to the brushes as possible will block a lot of the interference. Additional capacitors from each lead to the motor case my help, or may actually hurt. Experiment as required.

• Keep power wires short – Power wires act like transmitter antennas to broadcast the electrical noise sources. Keep them short, and cross the leads over each other with a twist about every six inches.

• Isolate the receiver – Put the receiver as far from interference as possible, away from ESCs and motors. A metal box around the receiver may help in difficult circumstances.

• Use a separate power supply for the receiver – If all else fails, try a separate battery pack for the receiver rather than pulling receiver power from an ESC lead or 5 volt supply from the main pack. The main battery may drop voltage under load and cause the receiver to loose the signal, or the power line may carry an interference signal directly.