Most of the units that I use or have seen used have sine signals. I=20 presume that the intent is to minimize coupling into adjacent pairs=20 (square wave is so much less expensive to generate than sine wave). Good luck! dwayne At 01:28 PM 5/15/2013, Bob Blick wrote: >30VAC at 1KHz? Sounds like a good excuse to get that old Crown DC-300A >from the shed! Thanks for the tip. I figured it would be something >simple. I have an old inductive "telephone handset amplifier" that I can >use as the receiver, I'll substitute the pickup coil with an antenna. I >probably should make a handle from a paint stirring stick to reduce body >coupling. > >Square wave, I assume? > >Thanks! > >Bob > >On Wed, May 15, 2013, at 09:40 AM, Dwayne Reid wrote: > > I have a bit of experience with this kind of stuff and my buddy does > > underground utilities location professionally (its his day job). > > > > 1) A couple of people have suggested using divining rods. Seriously, > > its worth a try. My buddy Russell (the guy who does this > > professionally) uses divining rods whenever he has to locate old > > sewer pipes that he can't connect his electronic tracing gear to. He > > says that it works well for him. > > > > Me: I can't offer an opinion. I haven't observed divining in > > operation nor have I tried doing it myself. But I absolutely won't > > discount its effectiveness. > > > > > > 2) The easy way to do this electronically is to attach a relatively > > high voltage 1KHz signal to one end of the wire. Grab any old audio > > power amplifier that can deliver at least 20 or 30 Vac (rms), ensure > > that the ground end of that signal is actually grounded (near the > > line if possible), and connect one conductor of that line to the > > output of the amplifier. Then use an equivalent of a "Hound" > > telephone line tracer. If you have one, use it. Otherwise, just use > > an audio preamplifier that can handle low-level mic signals. Attach > > a length of unshielded wire to the preamp's input and make sure that > > you can hear the 1KHz tone from more than a foot away. > > > > If you have an old PA amplifier with a 70V speaker output, use that > > to drive the line. > > > > > > I've got an old piece of Telco CO equipment called a "Jumper Tracer" > > - its used for tracing long jumper wires in an old-fashioned Telco > > Central Office. That's where all of the incoming subscriber wires > > wind up on large walls of dense punch-blocks and need to be > > cross-connected to the switch equipment. It uses a fairly-low > > frequency RF carrier modulated at 800Hz or so. The pickup wand has a > > coil wound on a short piece of ferrite rod at its end - this coil > > connects to the pickup unit with a piece of shielded twisted-pair audio > > cable. > > > > This unit is absolutely marvellous - I can trace wires that are > > inside conduit buried under six or eight inches of concrete. But if > > your wires are not inside metal pipe, its really easy to detect an > > audio-frequency electric field using that power amp mentioned above > > and a Hound listen unit. > > > > > > Finally, my company makes a couple of pieces of equipment used for > > detecting coating damage on buried pipelines. The transmitter sends > > audio-frequency current down the pipeline and the detector is a > > hand-held large-diameter walking stick that connects to the backpack > > that the survey guy is wearing. The pickup elements (there are 5) > > are circular coils that feed high gain, very low noise preamps. When > > all is said and done, we wind up with the depth of the pipeline (if > > it is buried or under water) and the magnitude of the current at that > > location. All of that data is logged along with the GPS > > coordinates. All the guy has to do is walk along the pipeline's > > path, swinging that thick walking stick from side to side. Every > > time the stick is exactly in line with the pipeline, he gets a beep > > from the receiver and the current measurements are made. The beeps > > help keep him on track when he doesn't know exactly where the line is > > buried or if he is in a boat. > > > > This gear is good for taking measurements several miles away from the > > transmitter. But its WAY overkill for what you need to do. > > > > dwayne > > > > > > At 10:57 PM 5/14/2013, Bob Blick wrote: > > >When the power company wants to follow the path of a buried cable, the= y > > >attach a gadget to one end and walk along the ground with another > > >gadget. Looks real easy when you have that $7000 pair of gadgets. > > > > > >Any idea what inexpensive thing I could modify to get a similar effect= ? > > >I don't need to do it on a live wire, and the maximum depth undergroun= d > > >is one meter or less. > > > > > >Thanks, > > >Bob > > > > > >-- > > >http://www.fastmail.fm - Send your email first class > > > > > >-- > > >http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > >View/change your membership options at > > >http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > -- > > Dwayne Reid > > Trinity Electronics Systems Ltd Edmonton, AB, CANADA > > (780) 489-3199 voice (780) 487-6397 fax > > www.trinity-electronics.com > > Custom Electronics Design and Manufacturing > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > >-- >http://www.fastmail.fm - Access all of your messages and folders > wherever you are > >-- >http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist --=20 Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .