In a few days, we will be having a small tower set up so that we can have internet connection in our rural home. We need to trench a cat-5 cable from the tower to our house but we also want to, in the same trench, run a power line out there so we are able to go farther with electrical items such as weed-eaters. What I wish to know is, how far down should the power cable be from the cat-5 as to not interfere with data signals? Both cables will be in separate conduits.
Possible duplicate of Can I run CAT5/6 cables parallel to electrical cables?, although that was more concerned with in-wall installation rather than buried. The general consensus from that thread seemed to be about 16" spacing (one wall cavity between studs) for typical #12 wire (servicing 20A circuits), though of course more distance is better. Assuming your power cable will be #12 or smaller (i.e., you're just planning to put a couple outlets over there, and no pool equipment or an AC condenser or something), that would be a good guide to use as well. Depending on what the conduit is made of, you could probably go a bit closer together to avoid more digging...but not closer than 12" (as per @Ecnerwal's answer)
There is, in fact, an applicable standard.
National Electrical Safety Code (NESC), Section 320 (B) (2),
Separations Between Supply and Communication Conduit Systems: Conduit systems to be occupied by communication conductors shall be separated from conduit systems to be used for supply systems by 75 mm (3 in.) of concrete, 100 mm (4 in.) of masonry, or 300 mm (12 in.) of well-tamped earth.
Only one of those is practical and affordable for a project on a budget, so I bolded it. You can be 12" apart at the same level, 12" above (power deeper, communication shallower) or a diagonal that works.
Type of conduit makes no difference - only the material separating the conduits changes the spacing required.