Where to draw power for ham radio install

[JonB]

I am adding a Midland GMRS radio and I want to plug my FT991 there as well in when I do POTA. I need 25 amps for the FT991 to be on the safe side. The 991 won't stay in the truck when I'm not doing POTA. My hot is fused at the battery and then there are fuses on the powerpole bus as well as the factory in line fuses on the radios.

I can understand needing heavier wire for an HF radio or possible additions. However, you likely won’t be transmitting on multiple radios at the same time, so current draw at any moment will like never exceed what the HF radio needs for transmitting - 25 amps.

Having multiple fuses in a power line is not a great idea. Think of your house — there is only one fuse per line. It’s there to protect the wiring and everything downstream from that. Same for your car - fuse the power leads at the power source — battery — and that’s it. There is an exception (of course) - if you have a low watt device in line which you want to protect. A line fused at 25 amps won’t protect a CB radio that only draws 3-5 amps on transmit. In that case, separate fuses for the CB would be needed.

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[KA5CVH]

I have to disagree with you here. First fusing the wire at the battery and having fuses in the power pole buss is just fine. The fuse at the battery only serves to protect the wire between the battery and the power pole buss. Nothing more ... nothing less. The larger diameter wire will reduce voltage drop, even though its only ~16 feet I will not see any voltage drop even running the FT991 at full power. Years ago running an FT100 mobile with 12 ga wire I could see a ~2 volt drop at the radio under full power with the engine off. The drop in voltage will only increase the current being drawn by the radio so a 22-23 amp load at 13.8VDC could become 25+ amps at 11 volts. Now each of my radios will be individually and properly protected at the power pole buss with very short leads. That's one of the advantages of using power poles. Now using your home as example. Every circuit in your house "IS" protected by two circuit breakers. The breaker on the branch line and the main circuit breaker at the service entrance. My A/C unit has three (3) circuit breakers. The main breaker, the branch in the breaker box and the contractor that install my new A/C put a third circuit breader/emergency disconnect near the compressor. And no I'm not putting a 25 amp fuse on a damn $30 CB radio. I've been doing installations on commercial V/UHF LMR radios, never mind all my radios over the past 40 years.

 

[JonB]

I have to disagree with you here.

Your comments are reasoned and intelligent and, while I may not agree with everything you said, your installation is top notch.

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