Carl--idea for your PI

[Randy Seden]

Far as signal enhancement for items that would fall in a particular range, if you could delay it by one period and add it to itself over and over (also a form of discrimination possibly?) wouldn't this allow us to hear targets farther down?.
I have a Seistronix Seismograph and it has the feature called "Stacking" whereby the weak signals are added to each other to improve the S/N ratio and that would seem to be the next leap in technology for our hobby of metal detecting.

What do you think?

Randy Seden
Simi Valley,CA.

[Carl]

Re: Carl--idea for your PI

In an analog PI, that's what the integrator stage does. In a digital PI, you could sample the preamp directly to an A/D converter, then do digital integration. Random signals (noise) will tend to cancel, correlated signals (targets) will add. This is definitely on my radar screen.

- Carl

[Randy Seden]

Re: Carl--idea for your PI

I wish you GodSpeed Carl as that would be so exciting to have! I done this using Bucket Brigade devices for the variable delay line as they are cheap and easy to use, plus Digikey carries the Panasonic line of BBD's.
In my particular case I delayed and subtracted the thru path with the delayed path to make a 60 hz comb filter and man did it work good! To avoid the echo effect, I found that I could just use a shorter delay time of one of the 60HZ harmonics. I then took a portable AM radio with the comb filter off, tuned to a far away station, turned on the comb filter and sat underneath the 16KV powerline in my backyard with complete absence of powerline hash (and this was using a LM380 to differance the signals on a single power supply as it was a last minute experiment!!).

Man keep us posted on this one. I can only imagine the kind of depth you could achieve by algebraically adding the signals that would ordinarily be below the noise floor!

Randy Seden
Simi Valley,CA