…Or not? Here’s a short post about often overlooked issues with supplying power to your mobile rigs (or any rig for what it’s worth..); Here’s the story I told to the owner of a Kenwood TM-V71…
First of all; let’s start with some basics:
- Ohm’s law
- Resistivity of a wire
- Contact resistance
We all know, that the higher the resistance, the higher the voltage across the component. Ohm’s law right? Imagine your power supply wire is a component.
Every gauge of wire has a certain resistance for a certain length. The thicker the wire, the lower the resistance. Choice of material plays a great deal in this as well.
Contact resistance. Often overlooked. A picture is worth more than words:
This is what contact resistance does. The fuse itself survives; but due to lack of good contact between it’s blades and holder – be it due to oxidation, bad design, or lack of pressure – the resistance will cause heat to be formed in the holder. Eventually degrading it further and further.
In short, the ‘repair’ of this TM-V71 was one of refreshing some basics to the user.. Lengths of thin wire, with cheap fuse holders and a plug that shouldn’t be there is a big no no.
Ham radio operators: keep power runs short, with thick wires, and premium fuse holders. Always. No exceptions.