for QRP Small Loop Antennas
This is the download page for a calculator of the efficiency of QRP small loop antennas. The calculator is based on the bandwidth method described by A. Findling, K9CHP, and K. Siwiak, KE4PT, in The QRP Quarterly. 
The page you are reading is a supplement to an article on this web site, “Measuring the Efficiency of a QRP Small Loop Antenna”, which includes a summary of the bandwidth method and examples.
The inputs for the calculator include the unloaded, -3 dB bandwidth that you measure with an antenna analyzer as explained in Ref. 1 and on a separate page. The calculator doubles the unloaded bandwidth to arrive at the loaded bandwidth and the loaded Q factor. You can scroll to the second page of the spreadsheet to see the formulas and intermediate results.
Here is a screenshot of the calculator:
To use the calculator you will need the free LibreOffice Calc spreadsheet program (Windows, Mac OS, and Linux) or Excel.
Libre Office LoopCalc-v1.0 (.ods)
Excel 2007–2013 XML LoopCalc-v1.0 (.xlxs)*
*The Excel version was formatted by LibreOffice Calc. Before it opens in Excel a format alert is displayed, and then it runs properly.
1. A. Findling and K. Siwiak, “How Efficient Is Your QRP Small Loop?” The QRP Quarterly, Summer,2012, pp 22-23.
Peter DeNeef, AE7PD, is an Extra Class amateur radio operator in the U.S. This Web site has no ads or conflicts of interest.
Email: HamRadioAndVision "at" gmail "dot" com.