I've used a similar technique I learned in the oilfield.
To solder a splice - 1) strip both conductors to be soldered about 1/2" and form a loop on one. 2) Stick the second conductor through the loop formed in the first and bend a loop around to join the wires. 3) Cut or break about 1/2" of solder/flux and lay on something flat, clean, and hard - 2 out of 3 is good enough here. 4) Use a hammer, flat rock, end of pocketknife, etc to flatten the solder until it is about 1/8" wide and maybe twice as long. 5) Wrap the flattened solder around the loops so that the join is covered by solder. 6) Strike a match, use a lighter, a torch, etc to melt the solder and flux into the joint. 7) Cover with weather-tight electrical tape and go on about your business.
Here's the US Army field wire splicing technique, pre-WWII.[1] No soldering at all, just tie the two wires together with a square knot, put a single copper strand through the middle of the knot, and wrap the strand around the wire on both sides of the knot for better conductivity. Then tape. When splicing a pair, the wires are spliced with the splices staggered about 6" apart.
Watching old training videos like this and documentaries[1], it's striking just how much better they are at conveying information.
They take their time. Shots linger, no jump cuts. No-one is driving around while talking, interspersed with random unrelated scenery shots. There are periods of silence.
At least on TV, most documentary style shows try to be so flashy and "cool", with lots of unrelated content that serves no purpose except to make it harder to think about what is being conveyed.
The difference lies on the purpose of the videos. Sometimes you want to convey a message, sometimes you want to sell ads. Each type of video is optimized for its intended use case.
A couple of other examples: an old US Army training video on the workings of various categories of firearms [0], and an old video on how transmissions work [1]. Both make great use of physical models of the mechanisms.
I would consider a soldered joint a bit of a different class of joint serving a different purpose. They are more physically durable, carry higher currents, and resistant to corrosion interrupting the link.
A twist or knotted joint is obviously fast and simple. But in the wrong environment it will degrade quickly. Are you laying a charge to be blown in five minutes, or laying buried communication lines to use for six months?
Easier than crimping or just preference? I know some fields require friction fit, some require soldering. In automotive we use friction fittings (screws, crimps) due to vibrations cracking solder.
Some aerospace applications required wire wrap for a long while because of its better vibration resistance vs solder. There were square profile bonding posts around which wire was tightly wound for a half dozen turns or so. The sharp edges of the post would thus make 24 points of contact, also biting through surface oxidation.
The wires we spliced were usually on long cables, more than 100' long (>30 m). The cables were laid out across pastures, through wooded areas, up drilling rig derricks, etc where they would remain until the data had been acquired or the well drilled. After that, they were rolled up and stowed for the next job or moved forward on the line and redeployed, again for several days at a time. The emphasis here was on maintaining the ability of the cable to be easily rolled and unrolled multiple times.
If mechanical splice connectors had been used then each cable would have a section which was much larger diameter than the unspliced cable diameter and if you didn't match the curl in the cable when you did the splice it would make the cable hard to roll since the coils would not lay flat. Some cables might accumulate multiple splices before aging out of the inventory and all those fat splices would make it hard to deal with very quickly.
The idea here is to produce a taped and sealed splice that has a final diameter that is as close to the unbroken diameter as possible so that there is nothing for the cable to hang on if it has to be pulled or dragged across the terrain or some machinery. Crimp splices, especially if you have multiple conductors cut will always produce a section of the cable that has a much larger diameter after splicing than the original cable and will be less flexible and therefore harder to deal with in the field. Any time you have a guy trying to shoulder or neck roll a cable that weighs more than 100 pounds you need to avoid complicating things.
When we did multiple conductor splices, up to 96 channels in my own experience, we had boards that were notched for each conductor pair and they were color-matched and spaced so that the entire splice would be a little under 2 feet long (.6 m) and all of it was looped and soldered. With a breakout box we could check continuity on each channel (a standard daily test) and have confidence that the splice was good before deploying the repaired cable.
I guess the easy answer is that you worry less about cracking solder than you do about being able to use the repaired cable as if it had not been damaged. Since each individual repair affected only an inch or so of the cable it had little effect on your ability to reuse the cable after the repair. The whole taped repair on a single conductor could be less than 2" long and would have a wrap of self-sealing rubber tape and a swipe with liquid tape to seal the ends. Very durable for all those chewies that cattle, deer, marmots, mice, etc. would add to your gear if it sat around in their neighborhood long enough.
I hope that explains it. By keeping the diameter of each repair near the diameter of the unbroken wire and spreading them along the cable if there are multiple repairs, the overall diameter of the cable ends up close to the unbroken diameter and the natural coil of the cable is unaffected.
You know, that would be a great way to fix most intermittent headphone problems, where you mainly need a strong mechanical result as much as the electrical connection.
When I was at school I was in the combined cadet force, and being interested in electronics I gravitated to Signals as it was known.
On exercises it was our job to provide communications and quite often we would lay miles of copper wires in the woods for the field telephones and join the wires together with these devices.
The black powder is some kind of thermite I think - lighting it would melt the solder in the copper tube, you'd push the copper wires you'd pre stripped into it and you'd hold it long enough for it to solidify, which was sometimes long enough to burn your fingers!
In the UK in the 80s the CCF had lots of surplus WW2 equipment. Beautiful valve radios and classic 303 rifles!
What would actual use case for this look like? The post mentions communication, but the usefulness of laying communication lines behind enemy lines seems like it would be minimal. Lines would be easily discovered and would lead right back to the spy or scout. The other use could be for demolition which I could see, but if I were a saboteur I would just twist the lines together as it's very temporary and time is of the essence.
Back in WW2 many communication lines were a single wire with an earth return ... years ago I was told a story (by people who were old enough to have been there) of doing that in the desert when they were facing Rommel .... guy picks up the phone, winds the generator to make it ring at the other end, someone picks up the phone answers "jawohl" .... sudden silence on the kiwi end, followed by scurrying around to find someone who spoke german so they could listen in.
Of course what had happened was that there were two parallel earth return phone lines on either side of the front, the lowest impedance path used both .....
Now this story was told to me by some old timers (people who could talk to you at the same time as they held a conversation in morse) - they told some great stories (all that I know of were true) - take it with the appropriate grain of salt
These were usually used at the front lines, to communicate with people stationed a little further back. Radio signals can be detected and eavesdropped, especially in WWII days.
It's not well-known, but the British tracked the Germans down to the unit level using radio transmission triangulation, and plotted their positions across Europe on giant maps. Even without decrypting signals, they knew a great deal.
The Germans were the first army to have radio on every vehicle, sometimes 3 for higher ranks. It was handy on the go, but leaked intelligence like a sieve when stationary for days, and the Germans were overconfident in its secrecy.
The British were warned of air raids even before takeoff because German pilots followed a procedure of testing their radio on the ground.
The mastermind behind the British effort built a similar system, but global, for the US, after WW2.
SR-71 flights initially used radios, but since Russian "trawlers" were tracking the broadcasts, later flights, including multiple refuelings, were done in radio silence.
There's a similar technique used in plumbing when you need to solder together two pipes.
There's a pre-made fitting (H cross section) which has solder rings inside. You press the pipes in and heat it until the solder comes out on both ends.
The technique needs an external source of heat but that's not generally a problem in civilian plumbing.
To solder a splice - 1) strip both conductors to be soldered about 1/2" and form a loop on one. 2) Stick the second conductor through the loop formed in the first and bend a loop around to join the wires. 3) Cut or break about 1/2" of solder/flux and lay on something flat, clean, and hard - 2 out of 3 is good enough here. 4) Use a hammer, flat rock, end of pocketknife, etc to flatten the solder until it is about 1/8" wide and maybe twice as long. 5) Wrap the flattened solder around the loops so that the join is covered by solder. 6) Strike a match, use a lighter, a torch, etc to melt the solder and flux into the joint. 7) Cover with weather-tight electrical tape and go on about your business.
It never failed for me.