A 16 ohm resistor would do fine (Brown, Blue, Black, Gold). This will put about a 300mA load on your receiver battery. You can figure out different sized resistors for different loads using Ohm's law. V=IR (Voltage = Current * Resistance). Simple Middle School algebra will yield R = V/I. Plug in receiver voltage for V and your desired load for I (in milli-amps, ex. .3 for 300mA). Your answer will be in ohms.