03-12-2016, 11:47 AM
Field telephones has already been discussed in another thread. This thread has focus on the connections between the phones.
The field telephone thread is here: http://www.pa2a.org/thread-field-phones-use-diagnosis?
Especially in dry areas this has been a tradition to do. What is needed for a usable telephone connection between e.g. to field (or other hand crank-) -telephones?
An electric connection made as a wire isolated from ground, and ground as return, or even better 2 wires, end even better, 2 wires twisted with some revolutions, the more, the better. (They used one revolution pr 4 poles in the old days, we use the same pr fraction of an inch today to carry data on the line) The to wires need to not have contact to each other.
What is a reasonable resistance in the loop? Hard to tell but a pair of awg # 20 will give a nice and stable connection for at least 10 miles.
Back to the fence wire. The steel wire used in a fence works well for pretty long distances, as long as the wooden poles are dry. If you want it to work well in rain, you have to put it on insulators, as one for electric fences, the neck of a bottle or other kinds glass or plastic doing that job. Just remember the sun might be tough to some kinds of plastics.
Now you have one wire from A to B, and you may use the grounds current carrying capacity as the other wire. This has some drawbacks, as high resistance, you may get noise from other things sending current trough ground, and in some cases it is possible to tap your signal. (not likely, but possible).
What makes a good ground connection? Metallic structures going in to the ground, as all kinds of metal pipes. A metal rod driven into moist soil. The army used metal rods in the latrine for easy connections. Your fantasy is the limit, but be careful with the grounding of the mains.
dsk
The field telephone thread is here: http://www.pa2a.org/thread-field-phones-use-diagnosis?
Especially in dry areas this has been a tradition to do. What is needed for a usable telephone connection between e.g. to field (or other hand crank-) -telephones?
An electric connection made as a wire isolated from ground, and ground as return, or even better 2 wires, end even better, 2 wires twisted with some revolutions, the more, the better. (They used one revolution pr 4 poles in the old days, we use the same pr fraction of an inch today to carry data on the line) The to wires need to not have contact to each other.
What is a reasonable resistance in the loop? Hard to tell but a pair of awg # 20 will give a nice and stable connection for at least 10 miles.
Back to the fence wire. The steel wire used in a fence works well for pretty long distances, as long as the wooden poles are dry. If you want it to work well in rain, you have to put it on insulators, as one for electric fences, the neck of a bottle or other kinds glass or plastic doing that job. Just remember the sun might be tough to some kinds of plastics.
Now you have one wire from A to B, and you may use the grounds current carrying capacity as the other wire. This has some drawbacks, as high resistance, you may get noise from other things sending current trough ground, and in some cases it is possible to tap your signal. (not likely, but possible).
What makes a good ground connection? Metallic structures going in to the ground, as all kinds of metal pipes. A metal rod driven into moist soil. The army used metal rods in the latrine for easy connections. Your fantasy is the limit, but be careful with the grounding of the mains.
dsk
dsk, proud to be a member of pa2a.org since Feb 2016.
A lo-cost electric fiber rope ha a resistance of approx 2.15 ohms pr meter (=yd) equals a copper wire of AWG #38 A triple galvanized steel wire ø=2.5mm has 0.3 ohms pr meter or equals a copper wire of AWG #20