OwenDuffy.net 

***EXPERIMENTAL***
This calculator allows calculation of the efficiency of a short / small vertically polarised antenna from field strength measured near ground level in the far field.
Use Directivity=3.0 for short monopoles and small loops. Some other Directivity values for common monopole heights over perfectly conducting earth are λ/4=3.3, λ/2=4.9, 5λ/8=6.3.
If the calculator reports "check inputs", the scenario is not possible, or not capable of accurate calculation.
The calculator uses Norton's f5 approximation for ground wave attenuation.
Example 1 is from (Belrose 1998) mobile whip on 7MHz. It Belrose's base data point from the curve fit of Fig 2, and yields a higher efficiency than Belrose calculated because he appears to have ignored factor As which is 0.8176.... his antenna is probably nearly 2dB more efficient than he calculated.
Example 2 is from (Griffith 1987).
Example 3 is from (Boswell et al 2005) 1m loop on 3.6MHz. It is one data point from Fig 6, and yields almost identical efficiency to Boswell's Table 2.
Version  Date  Description 
1.01  22/11/2015  Initial. 
1.02  
1.03  
1.04  
1.05 
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