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Originally Posted by Mike(Mont)
Just found this thread. I posted the same topic on another forum. I was planning to use an air core and 26-gauge magnet wire (not too difficult or thin to work with) to build a tuned loop antenna 2.5 feet square with 100 turns or about 1000 feet of wire. This way I can get by with one pound of wire a little wood and an old radio tuning capacitor. And it's not too difficult to build. Whether it will work or not to help detect an MFD signal line, don't know. I thought I could wear it like a backpack and have one more single loop of wire for an induction pick-up and maybe hook these wires to a set of L-rods or signal strength meter. This induction pick-up may not be needed.
What I do know is the tuned loop antenna is good at nulling out if you have it facing that direction. This might require you to move the transmitter to work around powerlines, etc.
I built a tuned loop antenna for the AM band range (seven loops of wire) and it really pulls in the stations, even with an old transistor 1960's radio. Of course newer radios probably don't need one.
I saw one of Carl's reports on a Raven LRL where there was a radio receiver and nothing much else. Anyway, I am going down a different path than the ferrite core antenna so it would be nice to compare notes. I still have to order parts so I'm a week away yet.
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This kind of air loop antenna has been shown on many amateur radio websites, and is said to be very good at tuning weak broadcast signals. It is often used in conjunction with an AM tuner to boost the signal the portable receiver finds. I have seen photos of a small portable receiver placed inside the loop in a location that produces a much stronger signal than the receiver can tune without the large loop in place. Of course there is an air capacitor that sets the frequency of the large loop, whether it is connected to the receiver or is used as a passive signal booster.
How well it works for long range metal detection, I don't know. But I do know it remotely resembles some coils Esteban uses in his experimental locators. The main difference is this loop is larger, and is probably designed to work for higher frequencies than Esteban uses in his coils. I would guess the larger size will provide an advantage in sensitivity, but may have some disadvantages related to pseudoscientific technical details.
Best wishes,
J_P