2.4GHz Warmer/Colder game based on signal strength
Different:  Place a GPS receiver in each "receiver". Program target coordinates in each rx. Go. Vegetation will affect the result.



RDF:

Location of transmitters by competing teams is traditionallyknown as "Fox Hunting". Traditional "Fox Hunt" transmitter hunters use directional aerial with nulling. Receivers CAN be very simple - essentially "crystal sets" in some cases. Others use very complex systems. 

Extremely good paper on Fox Hunting systems

Good but complex VHF system
 .. manual for:
Use of Mk4 Foxhunt receiver for pulsed signals

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80 m = 3.7 MhZ FH rx