Direction finding with RSSI

Question

I want to make a robot that can track the direction of the transmitter that is controlling it, for example to aim a camera at the transmitter. The robot vehicle will be controlled by a 2.4ghz NRF24L01+ link from within about 40 meters away. 
 I have seen some fairly simple methods to do similar kinds of tracking by comparing the RSSI from two directional antennas, for example here: www.rcgroups.com/.../showthread.php 
 It seems that I might be able to do this with a pair of nRF51822 modules, because they have RSSI available. If so, is it possible for the nRF51822's to just listen for the RSSI of the NRF24L01+, without interfering with the controller link in any way? I know the NRF24L01+ can transmit to multiple receivers, but could the nRF51822 make use of the same signal?

Janek Mann · Accepted Answer

The example of the antenna tracker you link to is different from your case for two reasons: 
 
 Their goal is to aim an antenna in such a way as to optimise the RSSI, not physically pointing at the receiver 
 The receiver is high in the air and as such is in near free space 
 
 In your case this is unlikely to work as RSSI is not strictly directional in the general case (affected by multi path, antenna pattern, etc etc). 
 Other than that, yes you could have the nrf51822 modules listen to the signal from the NRF24l01+, the modules won't interfere with the link much though the antennas could if placed in close proximity.