DIY utility locator?

[korg]

I'm a noob to SDRs in general. But I'm wondering if it's possible to use an SDR to detect a signal placed on an underground (non-live) wire using an arbitrary signal generator? I'd hook one pole to the wire under test, and another pole to a ground rod. This seems like the way most commercial utility locators work.

I just tried it by placing an Arbitrary Signal Generator (with a very rudimentary antenna) next to the RTL-SDR. Jumping into SDSharp, I couldn't really pick up anything at all. However, hooking up the same ASG to an oscilloscope will pick up the output.
As far as antennas, I was thinking that I'd hook the SDR up to a loop antenna in order to have a "void" spot where the line is.
And if the ASG signal isn't strong enough, I was thinking of hooking it up to either an audio amp or an RF amp before putting it on the line. This works when I hook up the ASG to a speaker, so I imagine it could work on the underground wire, as well.

As a bonus question, how could I modify this to induce a signal onto the line rather than connect the signal directly to the wire? I imagine it's just some form of directional antenna pointing directly down into the ground.

 

[K7MEM]

You might want to look into the technology used in a "Invisible Fence". There is lots of information via Google. I have a invisible fence at my house (3/4 acre), to keep my four dogs from wandering the neighborhood. I must say, it works very well, with three of the four dogs. My oldest dog (14) just doesn't seem to care. She doesn't wander more than 10-15 feet over the fence line, but it's like the warning signal and shock doesn't bother her at all.

As far as a Utility Detector, I let the county handle that. All my utilities (Electric, Gas, Cable TV, etc.) are underground. The county will quickly pop out and mark everything for us. I have had them out several times.

 

[mmckenna]

Inducing the signal on the pipe/conductor is usually done one of two ways:
Direct connection
Inductive loop.

I used to work in a job where I'd have to find buried telephone cables. The inductive loop worked well.

As for the receiving, you need a good antenna on the receiver end. Usually these locator systems work in the low single/double digit KHz range, so a loop/bar antenna would be a good start.