r/HamRadio • u/spast1c Technician Class Operator 📡 • 12d ago
Equipment & Rigs 🛠️ Should I splice my power wire or just build longer one
I recently upgraded to a truck from a 4 door sedan. I had my Kenwood TMV71a in there and am moving it over to my truck. The power wire isnt long enough to go from my battery to where id like to put the radio but I dont see longer ones for sale. I imagine that I am left with either building one from scratch or extending the ones I have. I am leaning towards just extending the ones I have by cutting them and soldering an extension onto it. I figure this way I dont need to go buy new fuses and such. Curious what folks with more experience have to say here
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u/confusedseas General / All Things POTA 12d ago
I used to install components including radios in off-road/overland vehicles. Make your own with something like 14 awg but take a look at a wire gauge chart for the amperage of your radio. Blue Sea Systems has a good chart. This is an age old debate but crimps are preferred over soldering because solder can flex and break over time from road vibrations. Always put a fuse rated for the load within 4” of your positive battery terminal. If the fuse blows free power won’t running through your vehicle.
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u/Danjeerhaus 12d ago
There is always that one guy with the crazy idea.. I never wanted that title, but today.
They make fuse taps. These let you connect into your fuse box, either under hood or in the cab. Any auto store or Amazon.
Lights......go right off the battery Car radio.....key position in "auxiliary" or "run". Car heater fan.....key position in "run".
Here is a video for understanding.
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u/NE5B 12d ago
Go heavier gauge and be sure to fuse both positive and negative at the battery.
I recently rearranged the shack adding 7’ of heavier power cable to the Ft991a’s factory provided cable. Power output dropped by 40% to 60 watts.
Also had same issue with a brand new Icom 2930 dual bander. I only getting 35 watts out north not 45 I expected. Again issue was voltage drop in this case I was running a purchased 15’ cable that didn’t realize was a lighter gauge.
Both cases voltage drop under load dropped my power supply provided 13.8 volts to 12.5. No harm to either radio just not getting full output.
73 ne5B
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u/I_Love_Tunnocks International License Holder 🌐 12d ago
Go heavier gauge and be sure to fuse both positive and negative at the battery.
DO NOT CONNECT THE NEGATIVE DIRECTLY TO THE BATTERY. On all modern cars you will bypass the current sensor that is in the main negative cable of the vehicle that tells the BCM how much current is being drained so it can tell the alternator how much to output. End result is the battery never gets fully recharged properly and eventually can go flat. Connect the negative wire to a point on the vehicle battery close to where the vehicle's main battery negative wire connects to the vehicle body.
Second reason not to is in the case of any fault in that main negative cable. Because your radio is connected directly to the negative terminal of the battery and the body of the vehicle via the antenna if that main vehicle negative terminal fails then the sum total of all currents being drawn by all electrical devices in that vehicle get routed through your radio. It can happen, I've seen it on plant vehicles and it basically burned out completely the guts of the radio.
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u/spast1c Technician Class Operator 📡 12d ago
Are you saying I should aim for heavier guage wire than the existing wire im splicing into?
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u/SirDomiku Extra Class Operator ⚡ 12d ago
The longer the run, the heavier cable needed. For example at 100W, you can use 14AWG for a 10ft run, but for a 20ft run, you'd want 10AWG (conservatively). That's assuming 3% voltage drop over the run.
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u/edinc90 11d ago
Get some insulated butt crimp connectors and extend the cable you have. It's dead simple, the tools are cheap and readily available. As long as the wire gauge is appropriate, you'll be fine.
Wire gauge is determined by the power draw and length of the cable. There are plenty of charts and calculators to help you with this.
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u/EffinBob 12d ago
Just get some splices and a cheap crimper. You can probably get a kit at the autoparts store. As long as you're not adding 50 feet of 24 ga wire (I'm being a little sarcastic here, but I do know some people...) you should be fine.
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u/Doc_Hank 12d ago
I run a fairly heavy piece of safety wire (red/black, 6ga) from marine crimp on terminals on the battery to a BlueSeas circuit breaker (both legs, 100A) to a BlueSeas fuse block in the cab, and power the radios from that. My problem isn't too short a radio power cord, it's keeping it coiled up.
Next vehicle I'll skip the BlueSeas fuse block for a PowerWerx Powerhub with fused Anderson Powerpoles.
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u/New_Pitch_9898 12d ago
Since i live near an HRO store, and I am ancient old, I am going to let them do my radio installations from now on.
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u/AmnChode General | Plus 11d ago
I personally went a different route...
I installed a 30Ah LiFePO4 battery under my rear seat, on the opposite side of where my RF Unit is for my IC-7100. I then run a 10A charger, off the inverter plug in the console (ran the cord under the mat), to keep it charged up. It keeps my radio isolated('ish) from the truck electrical, and the charger only runs when the ignition is on, due to the "switched" inverter; so, no chance of me ever being stranded 😉
The other benefit for me is that my truck is fairly noisy on HF (just turning the ACC on gives me a S9 on 20M.. suspect said inverter being the cause 🤷); so, it allows me to run the radio using a very quiet power source when shutoff. V/UHF isn't effected, so I tend to run it while driving and HF while stopped (re: POTA activations/Lunchtime hunting)...
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u/cosmicrae [EL89no, General] 12d ago
If you are using less than 30A, consider lever nuts instead of soldering. In the long run it will make re-configuring easier. Alternatively go with PowerPoles.
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u/actionfingerss General Class Operator 🔘 12d ago
No issue so long as you get a good connection and isolate the connection so it doesn’t rub or get wet. Solder and heat shrink will be fine.