Gunner Quinn
(Continued from Part 4.)
The Swedish M37 field telephone is an example of a good middle-of-the-road approach that is relatively lightweight, affordable, adequately durable, and mostly found to be in good operational condition. These are not as sophisticated and suitable for silent operation as either the TA-312 or the TA-1, yet they can be fitted with a 12 VDC grain of wheat sized red LED that pulses when an incoming call is made to the phone or a peizo buzzer that softly chirps and closely duplicates the TA-312 reduced volume ‘ringer’ merely by connect either to the terminals. Disconnect the mechanical ringer after installing the LED or piezo buzzer, or use cotton balls stuffed inside the bells to greatly muffle the sound to an almost inaudible level.
For the to common man, a single set of two field phones, one at the base station and the other at the primary lookout site could prove to be invaluable. If all other communications are inappropriate or to risky to use under a future threat situation, and when all other communication means and methods fail, the field phones will continue to operate.
Any adult occupying the LP/OP can master a field phone within minutes, and need not be overly concerned with radio communications security measures or radio discipline, in general. Unlike with radio traffic, they may speak naturally and use full-length discussions to solve a problem.
Two standard D-size batteries can keep the phones operational for up to one year if lightly used, in warm weather. Other exterior sources of 3 VDC can also be used. These are some of the desirable virtues and advantages of field phones. Because of the extremely low power requirement, merely stocking up on size D Alkaline batteries can eliminate the need for any power generation requirement to keep their comms up.
As a radio guy who is well acquainted with the serious issues of communication security in this day and age, I believe the extra expense and effort to purchase and install field phones is well worth it. I have made a sizable investment and spent about the same on field phones as I have on radio communications. Just as I would use my largest caliber rifles first, I will also use my most secure means of communication first as well, to avoid being targeted in the first place. At some point in the future, all potential sources of RF emission might necessarily have to be silenced, but yet I will still have rock-solid secure local communications, even with fairly distant neighbors via field phones.
JWR Adds: For some useful information on finding military surplus field phones, see this web page: Field Telephone Buyers Guide. And for more general information, including complete descriptions of many foreign-made field phones, see: The Collection.
Considerations and Alternatives for Permanent Installation
Commonly-available insulated wire, direct bury or less expensive light-gauge (24-gauge) standard copper telephone wire or any wire of heavier construction can be used. The current price and availability of WD-1 or WD-1A commo wire has steadily been rising over time, and a full DR8 spool of commo wire is not needed. This is because a full DR8 spool contains 1,000 meters (or roughly two-thirds of a mile) of the modern steel WD-1A, or on-half mile of the original and older all-copper WD-1.
[JWR Adds: Smaller USGI reels of WD-1A wire containing 1,640 feet (or one-half kilometer) are widely available from surplus vendors, such as Coleman’s Military Surplus.]
Ideally, any wire in a static position that will be maintained and used indefinitely should be housed in inexpensive schedule 80 PVC pipe and the terminal ends run out of a snorkel or pipe with a 180-degree turn downward turn after it emerges from the ground. This will prevent water infiltration.
If the wire can not be buried or otherwise protected, at least two wire pairs should be run above ground and suspended above the ground where possible. If run above ground, and if there is a need to span a creek or roadway, heavier copper wire of at least 14-gauge should be used as it has sufficient tensile strength to be suspended for at least 50 feet or more. Lighter gauge copper wire could be spliced in on either side of the bridge to reduce the cost, yet beware that any splice, or connection point represents a repaired break in the line that should be well weatherized and protected from water and corrosion especially if WD-1A that uses steel conductors are used. If only light-gauge copper wire must be used to span a sizable distance, then use cordage to support the line.
To adequately repair and protect a splice in a line, three wraps of self-vulcanizing electrical tape from 3M or shrink tubing can make a weatherproof repair possible that will protect the splice for many years. Soldering can also be used to a make a permanent connection that is mechanically stronger and protects the repair from oxidation. A redundant or spare wire pair should be run alongside the active line so that should there be failure in the first line, the second wire pair can be quickly attached in the event that the first wire pair fails in some way.
If the length of the run is determined, multiply that measurement by 2 or 3, so that we have enough wire to make at least two runs between each phone. WD-1A is made using low grade and malleable steel wire strands than can withstand abuse and used in all field conditions, however it is more prone to corrosion over time should its insulation become compromised.
A Solution for Degraded Wire Insulation
Aging and poorly stored commo wire, especially if it has been exposed to many years of sunshine, may have insulation that has become dry and brittle. Inspect commo wire carefully before deploying it. If the insulation is compromised, and no other substitute is available, then the wire pair can be separated and strung up as one would install electric fencing wire, using insulators. In fact, electric fence wire can be used as a substitute and as a stealthy method of installing field phone wiring. Only the positive side of the line needs to be insulated from the ground.
Field Expedient Field Phone Connection Options
The ground side of the phone wire does not have to insulated from the ground and in fact if the surrounding soil is conductive enough given adequate mineral and moisture in the ground, a metal stake or long copper grounding rod can be used to ground the phone and the ground or soil itself used as the negative conductor. This method can be used more successfully if the ground is well saturated with moisture and in shorter distance spacing or runs between phones. Once the ground dries out, its ability to conduct electricity and complete the electric circuit will increasingly degrade. This technique is a stopgap measure where there is a lack of wire to make a reliable connection. Electric or other metal fencing, or even a railroad track can be used as the ground side of the circuit.
Copper and Aluminum Wire
Where copper or aluminum conducting wire has approximately 6 to 8 times less electrical resistance than steel wire, and allows up to 6 to 8 times the distance without the use of a field phone repeater, it is expensive and more likely to break under the rigors of field use. It is best installed underground if the installation is intended to be permanent.
The expense of heavier copper wire that would withstand aboveground or belowground conditions without conduit for protection could be excessively expensive if the run is long. One could shop for a partial and lower-cost DR8 spool of WD-1 or WD-1A wire on eBay. Military grade commo wire, such as WD-1A has a tensile strength of 220 pounds and is so difficult to break that it is well suited for the roughest field conditions.
By the way, WD-1A has been known to stop vehicles when a large quantity of it becomes tangled in the front tires of a Humvee. It can even break the spindles that attach the wheels to the vehicles.
(To be concluded tomorrow, in Part 6.)
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