Campbell Scientific RF401-series and RF430-series Spread Spectrum Data Radios/Modems - Manual (Page 108)

Appendix K. RF401/RF411 Pass/Fail Tests
FIGURE K-2. Vertically Polarized 9 dBd 900 MHz Yagi
(ii) A collinear antenna should be solidly mounted in a vertical
position so that its omnidirectional “pancake” pattern is
horizontal. A metal or wooden stand can be used.
FIGURE K-3. 3 dBd 900 MHz Collinear Omni Antenna
(d) Set up remote RF401/RF411 with NO antenna and with antenna
connector 20 inches above floor.
(e) Arrange antenna distance apart according to following table.
TABLE K-1. 900 MHz Gain Antenna Test Distances
Antenna Gain
Over ¼ Wave
Power Ratio
vs. ¼ Wave
Distance Apart*
( Ratio Power ft. 5 × )
9 dBd 11.2 dB 13.18 18 ft.
6 dBd 8.2 dB 6.61 13 ft.
3 dBd 5.2 dB 3.31 9 ft.
-2.2 dBd 0 dB 1.0 5 ft.
* This assumes a signal strength vs. distance relationship of 1/d 2
K-6