Experts,
I found out more about my local test system/municipality. I will be meeting next week to learn more, and ask smart questions.
-The mains are mostly 16" diameter.
-They are all cast iron or ductile iron (DICL).
-They have a 3 mile (long?) section for testing, with key points already exposed.
-Though a small town (smaller than city), they are losing >25,000 gallons/month, and don't know where.
-They expressed a desire to know the state of key valves, and continuous (periodic) flow and other simple measurements.
-The first system I am inclined to test is induction communication via the pipes themselves, from one key point of interest to the next.
-Going down into LF (30kHz-100kHz) has been tested to have the best trade-offs of distance, power consumption, and penetration through typical ground materials. The HeyRadio uses 10W, for example, at 87kHz, and on a good day can get really good BW for voice and pictures to 500m. I'm only doing data, and the baud can be lopw and still not impact viability.
-I don't know the longest/typical distances these are, but I have access to the diagrams electronically to get an idea. Any place that needs sampling/testing, or has a valve of some kind, or another piece of equipment, is a prime initial location.
I've found that getting AF amplifiers that also go to ~87kHz is not too difficult, and their cost makes benchmark testing induction communication the first choice. Induction will also not be invasive (just a coil around the mains pipe). I haven't done hard-core radio theory in decades, but have been in the microcontroller circles these past years. I am hoping that the fact the iron pipes will conduct better than the surrounding earth materials will be a benefit, perhaps even allowing the earth ground to be a form of return if needed (meaning making a circuit including ground, instead of just a loop/coil at each end.
Does anyone have any questions I should ask of my 'guy on the inside'?
Does anyone have any suggestions for cheap rigs to either build from schematic or modify a ~10w audio amp for benchmarking?
Does anyone want to make any official guestimations on how well (or if) it will work (meaning distance of signal detection)?
TIA!
pat