ELF detector

Use an opamp with low 1/f noise, and a loop antenna.

And a Pixie tube, of course.

The zero on the bottom end of the range can be trouble.

You can get GMRs from Digikey.

You didn't give enough details. How big does the loop have to be to do the "0-" part of the range?

A 100W light bulb does a good job for me. Its sensitivity extends all the way to 60Hz, in fact.

Tim.

I think that can be fixed with suitable software.

Ed wb6wsn

Older hams know that 100 Watt light bulbs have a frequency response to at least 50 MHz! But they must roll off badly above 1 GHz, because they never show the power I'm really putting out!

Ed wb6wsn

I doubt software can do it. You need to divide by zero. Most programmers have a hard time writing code that does that successfully.

I read in sci.electronics.design that Ken Smith wrote (in ) about 'ELF detector', on Sat, 25 Sep 2004:

IF DIVISOR = 0, THEN RESULT = 1E+38 ELSE RESULT = DIVIDEND/DIVISOR

It's the order in which you write it that matters. (;-)

Depends on the sensitivity you want. Obviously, you cannot make a loop any where near 1/4 wavelength...

ORDER?????????? What is *that*??

Precisely, solved in Basic, circa 1968! Or in Fortran, even earlier! That's how coders solve those pesky little "special cases".

Ed wb6wsn

Ask your friendly local Marine sergeant.

I read in sci.electronics.design that Ed Price wrote (in ) about 'ELF detector', on Sun, 26 Sep 2004:

There's a bit more to it. My pseudocode produces an extreme outlier result, which the user really ought to pick up. It does NOT produce an error message that stops the program. Of course it can be extended to produce a *warning*. Stopping the program for a recoverable error is, IMHO, really rather stupid.

Note that you've arbitrarily chosen to use a very large positive number for the result, even if the dividend is negative. I prefer math that saturates in the appropriate direction. Sometimes, even with division by zero errors, you can get it right. The sign tends to matter quite a bit in control stuff.

Best regards, Spehro Pefhany

John Woodgate writes within:

IF DIVISOR = 0 THEN PRINT "Division by 0!" ELSE RESULT = DIVIDEND/DIVISOR

I read in sci.electronics.design that Chaos Master wrote (in ) about 'ELF detector', on Sun, 26 Sep 2004:

But that overflows the column in a table of results, and is liable to scramble the whole rest of the print-out. I speak from experience! (8-O(

On Sunday 26 September 2004 12:23 am, John Woodgate did deign to grace us with the following:

Gee, John, do you still punch your Fortran onto Hollerith cards?

;-) Rich

Friendly?

Charles