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WTB - Older Garrett BFO (- Classifieds)

by Bob Sickler, Friday, September 16, 2011, 08:44 (2560 days ago) @ Carl

OK Carl, you asked for it!;-) ... My interest is purely Garrett nostalgia from a collector's viewpoint I guess, but I have been doing some tests lately with the little Garrett Hombre BFO I found in a yard sale. The test is all about how well the BFO's deal with concentrated iron masking.

This test has been indoors and hardly a true scientific test, but just these simple results floor me. I have a huge old rusted washer (as in bolt & washer) in my test box inventory. Over the years it has literally shed rusted iron chunks. I also have several old square nails of different sizes as well. I dump these on the floor of my house which has plywood underlayment below the carpet with it's own common nail heads. In the slightly spread out pile of iron chunks and nails, I later drop a Barber dime in the middle... But first I tune the BFO to the Metal side and keep the threshold beat rate a little faster than normal. I use the 8" coil of the Dual 4"/8". Sweeping over the pile of rust and nails only, the BFO threshold frequency or pitch drops thus indicating iron. Then I drop the silver dime in the mess and sweep over again.... Magically the BFO sees the iron, but it signals with an increase rise in threshold pitch telling the presence of an upper conductive metal. Almost as if it reads the iron and subtracts the dropping effect off of the dime's positive.

If I take my Etrac, or any other newer digital detector with a large coil (10-12") enabled with discrimination levels to reject the iron, and I pass over the iron alone it nulls (quiets) the threshold or does not respond (silent search types) as it should. But when I add the dime to the mix, these detector fail to read it or the iron rejection overpowers (masks) the small silver target. But, if I take my old Garrett ADS Groundhog at about foil rejection (which includes most small iron) and do the same test, it will signal the dime clearly as well. Only when I really ramp up the discrimination on the Groundhog does it fail to read the dime. Analog detectors of yesterday have some disadvantage in terms of depth in heavy mineralized soils, but their ability to lessen the effects of iron masking is a clear advantage!

I hunt mostly old home foundations of early abandonment and many times the depth of the items found that date parallel with the origin of the dwelling remnants are not really all that deep compared to what I find in parks that have high traffic on the grounds. Yes, I sometimes kick away several inches of matted leaves to reach soil, but I dig not terribly far down to make good finds at these old sites.

Do you see my logic and possible use for this type of metal detector? I've used BFO's for years, but I never gave it any thought to why I was finding what good items I did when I had nothing better or worse to compare it to! Now I do and it pauses one to think. I only wish today's manufacturers could re-invent the BFO concept and give it a little more depth in minerals. You say Pulse? I don't think pulse detectors are all that great at signalling with some identification of iron. Fact is you can dig for miles to find a "Bobby-Pin". The BFO's aren't so sensitive to the small iron.

All I can say is find an old BFO and try my test and you will know my interest.

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