We all have seen or been part of similar stories - where you start to paint a stripe on your car and end up making it wider and wider to cover mistakes until you end up painting the whole car. A simple job for a computer that grows till its enough to make you call for reinforcements. Often these projects could be better kept under control if you could use a bit more planning and research. Old man Murphy and his law comes into play far too easy some days. Lets take a "simple" two way radio system installation I was involved with about 35 years ago for our first example.
A base station radio in one spot, and another in a spot a small distance away - and workers who will use some portable radios as they work between the two locations. We then find that the "rub" here is the fact that one of the stations is 1100 feet underground.
Ok - but all we need is to talk the 1100 feet down the shaft - straight down, all "line of sight" and you could just about holler back and forth if the fans and machinery were not making too much noise. The portable radios just need to work inside the shaft area - again simple easy line of site for radio. Now my boss knew that rock either absorbed the radio signals or bounced it excessively - he was not (if i remember correctly) sure which it was. So we make it simple - by putting the topside antenna down nearly 50 feet into the shaft, and the bottom side antenna up inside the shaft about 50 feet, the two locations will be only 1000 feet apart. To be extra sure we have lots of signal to blast down this 1000 foot shaft - we put some yagi antennas at each end - with probably 9db gain - making the signal level in that shaft really strong. We even put the yagi antennas in some fiberglass shells to protect them from the potash salts that accumulated everywhere. Did it work?
No. We checked everything top and bottom and just could not believe that it would not communicate. We took a high powered portable radio (lunchbox type) and started down the shaft - slowly and checking with the topside base station every 50 feet or so. At about 400 feet - we lost contact with the top side - and about 400 feet from the bottom we could talk to the bottom station.
Please keep in mind that the gentleman who bid and ordered this system, my boss in this job some 35 years ago, was no dummy. He had seen and worked with 2-way radio for many years and put in many antenna systems for many different types of systems. But he had apparently just decided to go at this with lots of signal and hope for the best. It may be that the signal level caused part of the problem - I have never researched it fully myself.
Did we mention that this location was an hours drive away - and we did many trips back and forth to try this or that and to be 100% sure that we had done what we could. We were also slowing down some of the regular crew at the mine - as they had to suspend some of the loading work while we were in the shaft. We had to have "babysitters" to be with us for safety sake - even after taking a half day course on mine safety. One of the funnier moments was when I walked near a hole in the floor - it had to be smaller than 10 inches square, and had a pipe fence around it to be safe and keep anyone from twisting an ankle in it. The "sitter" grabbed me and pulled me away - worried that I might fall in (somehow) this small hole. I tried to explain to him how I routinely worked on radio gear mounted in boxes 1500 feet up on a 1830 foot tv tower. Working there where only a few places were safe to stand - and they were just inches wide. Everywhere else, was a long way down. His concern was a bit much to me at the time.
So its important to research and not assume - to look ahead and if you have not done a job like one before - you should check it out fully before you do it - or even quote such work. And - the more sizeable the job, the more this can apply. I will explain how that worked on a larger network job in one of my next blogs on this subject.
The mine shaft ? Well in digging a bit more my boss found that there was a certain type of coaxial cable that had a slot cut in the shield under the plastic jacket purposefully to allow some signal to leak out all along the length of the cable. So we went back with a 1000 foot roll of this cable - seems it was about an inch and a half or 2 inches in diameter - so this was a huge spool of cable. We hooked it up where the topside antenna was previously, and using a gun that shot nails into the rock, we unrolled the cable and nailed it in every 3 feet all the way down. This was in winter and the air and moisture coming down the shaft made for a chill factor that is well below freezing. We had part of the shaft crew with axes chopping the ice out of the corners of the shaft as we put the cable in place.
Part of the way down we had a problem. The shaft crew was using a pull cable in the shaft to ring a bell upstairs. They have a very complicated series of long and short rings to indicate to the lift operator what they want to do - including going slowly and stopping every 10 feet. However the ice problem we were fighting froze up the cable up above us somewhere - and standing orders for the lift operator would be to pull us up out after so many minutes without any contact. If we did that we would have to cut the expensive cable and come back another day with more.
Fortunately that time, we did plan ahead - and had brought one of the portable radios along to test with - and were able to shout on it enough to get someone to tell the lift operator how to proceed and we could finish the job.
The next time I post about such jobs - we will look at a rather large network and computer setup I helped with and how a simple oversight caused lots of headaches and extra labor. Meantime - think it out, think of what could go wrong - plan ahead and if possible have a plan B waiting if you can.
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