Friday, March 2, 2012

Loop Calculator One

Loop Calculator One is a program which will display detailed information about coils, including accurate inductance for short and long coils of many types. It is especially tailored for inductance calculations of polygonal-shaped mediumwave receiving loops.


To download, see the link at the top of the right sidebar under LATEST PROGRAMS. The sidebar at the top right will have the most current link in case the program is updated. The link will change in the case of an update, so I would avoid copying and pasting it into a forum or other web page. Come to the main page of this blog instead.

Click image to enlarge.


Being a mediumwave DXer and wanting to construct my own passive loop devices, I was unhappy with virtually all the web-based coil calculators found on the internet. They used either inaccurate formulas, or formulas that weren't even designed for large but very short polygonal coils like our passive loop, or they didn't correct for internal inductance, self-inductance, mutual inductance, or self-capacitance. The few stand-alone programs out there didn't satisfy either. I set out quite some time ago to accumulate information, formulas, and data to start writing the inductance calculator program. The going was slow. Investigating the history and ferreting out the accurate information took much more time than I thought.

The result was and is Loop Calculator One. Four main formulas (plus two extras) are presented. Two formulas build on the fact that a polygonal loop inductance can be calculated by figuring its equivalent circular size using area and perimeter equivalents, with modification, then calculating the inductance from that as if it was a circular loop. H. Nagaoka's old inductance formula and Wheeler's 1982 Continuous formula, both for circular coils, are used in this way to arrive at surprisingly accurate results. More surprising, I discovered that Nagaoka's old turn of the twentieth century formula using Lundin's formulation of Nagaoka's non-magnetic uniformity coefficiant holds amazing accuracy across a wide range of loop form factors. An excellent treatise on calculating the modified equivalent circular loop radius of a polygonal form can be found at electronbunker.

The remaining four formulas are by F. W. Grover of the NBS (National Bureau of Standards). In 1929, Grover offered two remarkable formulas for solenoid and flat spiral polygonal loops in his paper, "The Calculation of the Inductance of Single-Layer Coils and Spirals Wound with Wire of Large Cross Section", Proceedings of the Institute of Radio Engineers. His two simplified versions for polygonal loops appear in the book "Inductance Calculations: Working Formulas and Tables", (Van Nostrand, 1946 and Dover, 1962 and 2004). Loop Calulator One also presents these four formulas.

All formula results are corrected for self-inductance, mutual inductance, internal inductance at frequency of operation (which is user-definable), and self-capacitance (by check box). Much additional information is displayed about the loop or coil, including calculated tuning range from a user-defined variable capacitor, the coil's form factor, Nagaoka's constant, and more.

Wire gauge can be input directly in American Wire Gauge format, or as a user-specified diameter. R. G. Medhurst's calculated self-capacitance estimate is displayed and can be user-entered to see how it effects the tuning range of the loop.

As a side bonus, a separate formula box can calculate the actual self-capacitance of the loop using the low and high capacitor values and the actual discovered low and high tuning range by using a receiver.

Small circular "radio" (long) coils can be calculated. The Nagaoka and Wheeler formulas are used in these calculations.


Install is simple. Download the .zip file and unzip. Click on the LoopCalculatorOne.exe file to run. This program makes no registry changes and saves no data to your hard drive. It has been developed and tested in Windows 7. It should work fine in Windows Vista and XP environments, and Windows 8. It is written in the old standby Visual Basic 6.

Included in the .zip is a readme.txt file. Be sure to have a look. Also included is an American Wire Gauge chart showing wire diameters.

I hope you enjoy this program and find it useful.


Scotland said...

Terrific program; I'd been looking online for some time for such a calculator. I am still seeking a general background to loop design, though. E.g. a graph of how sensitivity and nulling depend on the separate parameters of number of turns, total wire length, wire separation, loop dimensions. Why do some loop designers use a separate pickup loop, while others do not? Is there a heuristic for trading off number of turns, loop size, loop width?


Hi Scotland,

Thanks for your interest and kind comments about Loop Calculator One.

One document that I found in my files explains a lot about passive loops. It is actually a compilation of a number of documents and something I found some time ago on the internet.

Some general rules and observations:

1. The larger the dimension of the loop, the greater sensitivity. Some in the ultralightdx group have built 9 foot loops!

2. I usually go for more turns and less capacitance, it seems to result in greater sensitivity. I also believe that a wider loop edge results in worse nulling ability. So you need to strike a happy medium here - if you use more turns, keep them close together.

3. Keep your coil turns spaced as perfectly as possible. I personally believe this makes for better nulling ability.

4. Read up on coil "Q factor", that also effects the selectivity of the loop.

5. Separate pickup loops are sometimes used to match impedances (like when directly connected to a radio), or to isolate the main loop. Isolation can result in better performance characteristics like nulling and selectivity.

Check out the posts in the Yahoo ultralightdx group. A lot of loop work going on there, and some informative files to download.

Good luck and enjoy learning about loops!



F5VLB said...

I have unziped the software but I got a : field is not numeric range is 0.025 -72 ok

When I click on OK I got a excecution error '5' ... what am I amissing e? your soft seemes exactly what I need to calculate my double loop system. best regards from Britany JOHN F5VLB



It seems like you have entered a non numeric character for the coil depth (length). The Imperial range is 0.025 - 72 inches. Be sure to also use a decimal point rather than the comma (,).

Hope this helps.