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Written by K9XD   
Monday, 21 February 2011 19:30



Here is a different way of handling your DC power distribution. You can build this the way I did for around $100 or build it using 3AG type fuse holders for DSC01366less. The idea is to make the main fuse what ever the max current is of your power supply. Then fuse all of the equipment according to it's specified current draw. A good size power supply would be 50 amps. This1 will cover just about anything you throw at it. Make a common point negative buss and isolate it from the box with stand off insulator. The box will get a green ground wire to your station ground. This way if something shorts to the box your not pulling current though your equipment DC ground paths.

If your going to do a battery back up for your station, a good idea if you have unexpected outages, it gets a little tricky. Use a sealed tel-co battery not a vented typelike a car battery. There are not to many power supply’s that do Float. Float is where the battery charger voltage hovers when the battery is fully charged. This way   you will not over charge the battery. The battery will have a spec for float. Make sure the power supply has a voltage adjustment so you can set the voltage to this. But wait there's more!DSC01367

Now this is very important! Unless you have a power supply that is spec to float, then you need to do the following. You will need to add a relay / contactor depending on the current and a timer. See the picture of the inside of my Austron 50M. I added a simple HVAC timer from a supply house that will delay the 100A contactor I installed in the power supply. When the AC drops the RY /DSC01368 contactor open. When the power come back on there is a delay of 2 minutes. This is to disconnect the battery from feeding DC into the power supply and damaging it when it is turned back on. If you do not do this I will guaranty you will damage your power supply. You can put it outside the power supply as well. I just had room in the power supply and put it there. If I built another box I would put this in the fuse box instead. You also may want to consider a second RY that will be for low voltage.  This will disconnect the battery once you drop below 11 volts. You don't want your radio on a battery dieing a slow death. Voltage drop is big problem because most hams under estimate the wire size. I can tell you from experience that for 20A with a wire length of 12 feet you will need to run #6 wire. I see 1/4 volt drop at the radio. With the factory #10 wire loom that cost my $30 I had a 2 volts drop. I noticed this when I turned on the radio all happy my cable came and I only saw 80W out instead of 100W. Most of the visuals of the radio are below 10V so you never see the drop, like dimming display. But the PA is looking for 13.8 for 100W. The bottom line is measure the voltage under full load at the device and if it's more the ½ volt drop size the wire up, bigger is better. If you need more detail or have questions let me know. 73's K9XD




Last Updated on Tuesday, 22 February 2011 19:57