Receiving Directivity Factor (RDF) helps determine the performance of antennas on receive, this is useful with lower HF bands under 10 MHz where noise becomes an increasing problem. RDF is the difference between the peak forward gain and averaged gain in all directions.
RDF value can be calculated using an EZNEC model:
- Set plot type to 3D, click FF Plot, average gain displayed at the bottom of EZNEC window.
- In the 3D Plot window click View > Show 2D Plot, the peak forward gain is displayed.
- Subtract peak gain from average gain, this is the RDF figure.
Here's an example using a LoG (Loop on Ground) phased array I modeled:
Click for lager image
Average gain -37.06 dB minus peak gain -28 dBi = RDF of 9.06 dB, which in the world of RDF and receive antennas is respectable.
Reason I post this, is it's easy to find pages discussing RDF and figures of various antennas, but only two places I found mention how to calculate it - Receiving Basics and The Challenge: Receiving Antennas.
More about The RDF Metric.
More can be found by searching for Antenna RDF or Receiving Directivity Factor.