My outdoor AM transmitter is fed power and audio via an underground line which is an abandoned 120 volt 12-2 with ground type UF power line. This has been underground for 26 years and has worked very well as my STL.
Yesterday the current meter which I use to monitor the transmitter feed indicated erratic current changes and finally indicated an open circuit. My best guess about the failure is that we have chipmunks burrowing in the back yard between the house and the transmitter and one burrow is near the line run. They probably have gnawed through the line.
One regret is that the line wasn't live with 120 Volts when their little rodent teeth violated the insulation.
A new feed line is planned with some protection this time. I have some 1/2" CPVC pipe which I plan to use as a conduit for burial and will fish the line through this.
If you plan any underground wiring consider means to protect the wiring from Chip & Dale and other hazards such as a spouse who likes gardening.
Neil
How many feet away from your house is the transmitter?
I'm just about ready to plan laying cable for about 75 to 100' way up back for the Ultimate Antenna per PhilB's recommended method as posted elsewhere on this website.
A buried PVC pipe will need to be kept water-tight and it will be necessary to learn the art of fishing cable for all that distance.
Also Neil, you've previously made recommendations about adding lightning sagety to wiring as it enters the building, so I'll need to scroll around and look for that or perhaps ask for a repeat.
The idea of hearing the AM signal coming from as far away as possible is very exciting, and I might start living in a tent so I can get even farther away.
An easy way to get a line through the conduit is with a vacuum cleaner.
Make a tiny parachute with light weight plastic like a shopping bag. Tie a strong, light weight string like kite string to it. Insert the parachute and string in one end, attach the vacuum to the other end.
You'll be surprised how quickly the string is sucked to the other end if all goes well.
Then you can use the light weight string to pull the wire.
We don't have carpeting and thus no regular vac, and the shop vac I had was too loud so I gave it away.
Is there a smallest size vac that will work as a string-puller?
that is brilliant - thank you
This probably wouldn't work for you but
it works with larger conduits and pipes,
I guess.
I've never done this, but my friend told me:
Get a little battery powered toy car, put a
string on it, and let it drive thru the pipe.
When it comes out the other end, you can
grab the string and achor it on the far end.
Then you can attach wires onto the begining
of the string at the start of the pipe. Then you
can pull through bigger and bigger wires.
It's a fun little idea to tell, anyway.
bvruce, DOGRADIO
With my luck it would be rush hour in the pipe and the toy car would hit a toy school bus. A toy police car would pull up and and ticket me for pulling a "too long load."
I know how things work.
We usually use a shop-vac. Most of the conduits we fish are between 1.5 and 3 inch.
I'd think a 1/2 inch conduit wouldn't take much. Trick is to get a good seal.
If you have an air compressor you could try to blow it through but its harder to feed the string with the hose in the way.
Way back when I watched a telephone installer fish wire through a conduit. He had a small spool of HTCC (high tenacity cotton cord) on a bobbin with a mushroom shaped end and this was pushed through the pipe with compressed air from a small hand pump. Sounds similar to MRAM's suggestion.
My install will involve 10 foot lengths of CPVC which I bought years ago with this in mind for my ham antenna feed but that project never got off the ground (or under it). The plan is to fish some cord through the 10 foot length, then through a coupler, then through the next 10 foot length. The two pipes will then be glued together via the coupler and the cord will be through both. The process will repeat for each 10 foot length as it is added.
Long runs can be hard to pull and the process can be helped with a soap solution or talcum powder to lubricate the wire. Pull boxes are sometimes used at intervals to shorten the pulls.
My total run is 40 feet. When the cord is used to fish the wire another cord will be pulled along with the wire. This will leave a cord in the conduit for future additional wires. I have learned to always leave a cord in a conduit or raceway so additional wires can be pulled without having to do any fishing.
Re the safety, the ground wire is bonded to the house ground at the point of entry. Fortunately for me the entry is very close to the electrical panel and the house ground stake wire is right there. The remote transmitter is also grounded to a buried wire. The power and audio lines are connected to ground at entry through spark gap tubes which conduct at 70 to 90 volts. These are inexpensive (about $1 ea. if memory serves me) and they are available from Mouser.
If your point of entry is not near the electrical panel then I recommend running a heavy (#8 copper or #6 aluminum) wire from the electrical panel ground to the entry ground. Some use a ground stake at the entry but I don't like this because in the event of a lightning strike there will be a high potential difference between the entry stake and the house ground stake. This voltage will appear in and on your radio equipment. By using the house ground only this voltage is minimized.
In any case your local codes will apply and may differ from what I described.
Neil