The National Radio Club has many publications on loop antennas, and those can answer your questions and more.



On Monday, November 26, 2012 12:10:13 PM UTC-6, rickman wrote:
I've been doing more work on the low frequency tuned loop antenna and

have two problems. One is that I can't find any info on how effective

the antenna will be in relation to the design parameters. That would be

the diameter of the loop, the number of turns and the spacing of the

turns. From the formulas I find for inductance, I would guess that the

spacing of the turns will want to be as small as possible, but I'm not

sure the factors that optimize self inductance are the same as what will

optimize antenna effectiveness.



What equations determine the signal strength from a low frequency tuned

loop antenna?



The other problem is finding an accurate formula for the inductance of

this design. I've found a number of equations for coil inductance, but

most are for coils with length longer than diameter. One I found

doesn't say what it's limitations are and doesn't agree with the others.

In fact, I can't find two formulas that approximate each other over

the range of interest which is 1 to 20 turns or d/l from 4 on up.



I've consulted the Radiotron Designer's Guide, Nagaoka's and Lundin's



papers on inductance of coils as well as a number of web pages. I'm

getting tired of looking... Is there a reasonable formula for

calculating the inductance of a short coil that works for a number of

turns from 1 to 20?



Rick