Directional antennae accuracy

[NeroRavencoat1999]

Of course most fpv Tx modules today operate in the 5.8Ghz band and there is a variety of directional antennae on the market for Rx. My question is how directional are they especially close up within a few feet of the Tx?
My purpose for this is possibly using the Tx as a locator beacon.

 

[Fluburtur]

Depends on the antenna, 7 turns helical antennas and biquad antennas have a beam of around 50°

 

[Hai-Lee]

Each directional antenna has a beamwidth measured at the 3db points, (half power point). Added to this main beam is the number of side lobes, (each a beam in itself).

To obtain accuracy it is always best to do a search for the PEAK power bearing from 2 or more separate locations and where the beams cross is the area of the source, or where you should search.

Beware of cases where the strongest signal is actually just a strong reflection because the signal path between you and the source of the transmission can be blocked by obstructions. The use of a number of different measuring locations can reduce this reflective source effect.

RDF, (Radio direction finding), can be an art at times if done at ground level. If you have a RDF setup in a drone then much quicker determinations can be made.

Have fun!