Any one who has EVER coiled wire, coaxial cables, audio cables or even a hank of rope knows UNCOILING it has at one time or another created a “rats nest” of tangled mess that will increase your blood pressure, makes you exceedingly cranky and often has caused Tourettes-like symptoms. Fighting an unruly coil of coax or audio cable wastes a lot of time when setting-up a gig, a Field Day site or even coiling a power chord at home! Having spent years working in television studios, control rooms, and other audio gigs on a daily basis, I learned early on from the engineers that there is ONE way to coil cabling… W2AEW shows that in his video! (P.S. Engineers can be especially grouchy if you don’t coil correctly and THEY get to untangle YOUR improperly coiled rats-nest from a previous gig tear-down as they work on an important production. Time is money.)
This video shows how to measure the value of unknown capacitors and inductors using your oscilloscope and a simple pulse generator. There are many ways to do this, but this video focuses on just two basic techniques. The video was inspired by this blog post on scopejunction.com:
The techniques are very simple, and are a good example of basic principles of RC and LC circuits. Another bonus is that it shows another use for the fast-edge pulse generator that was shown in a video I posted several days earlier on making your own basic TDR:
The capacitors are measured by simply measuring the RC time constant, and the inductors are measured by making a simple LC tank circuit and measuring the resonant frequency.
This video shows one way to use a scope and function generator to measure the length of a piece of coax transmission line as well as estimate its impedance. It uses a “poor man’s TDR” type of measurement by launching a pulse into the coax and measuring how long it takes to return after being reflected by the open circuit end. This same technique can be used to determine the distance to a fault (open or short). A simple method for determining the impedance of the line is also shown.
This video touches briefly on transmission line and reflection theory, but is definitely not intended to dive deep into these topics. There are literally books written about this topic – so that won’t be covered here.
If you are looking for coax, antenna wire, connectors, rotor cable, insulators, rope or the tools to make antennas Davis RF Company is a place I like to use.
Click link below to go to the Davis RF website…
Need to figure out what cables to use or what the pinout configuration should be? This is a nice resource for just that!
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