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Author Topic: 2M radio in car - "add-a-fuse" fuse taps for DC power?  (Read 4358 times)
N6GQ
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« on: January 02, 2017, 12:40:18 PM »

Hey all, I'm going to put a  FT7900R in my wife's 2016 Honda Pilot. She loves the car and is very resistant to me out there drilling a hole in the firewall or cutting the existing grommets on factory wiring harnesses that go through the firewall, so I though I'd try the "Add-a-Fuse" fuse box taps to get DC to the radio.

From what I read, these fuse taps are good for 10A which is enough for the 7900R at full power (max draw 9A@12V). It would mean I just need to get the DC cabling to the fuse box inside the car (near the driver's left leg) and I should be golden. Antenna cabling is easy based on the mount/antenna being used.

Anyone tried these fuse taps and have any suggestions one way or other? Seems to me it "should work" but I know there's always gotchas.
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WB2EOD
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« Reply #1 on: January 02, 2017, 12:50:04 PM »

Bear in mind that a radio like the 7900 draws maybe 12-15 amps in transmit. 
Best bet is direct battery connection with fuses close as possible to the battery end.
Whatever you do DO NOT use the "power socket". 
Regardless of how well it is fused, the connection is good for maybe 7 amps. 

73
WB2EOD
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N6GQ
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« Reply #2 on: January 02, 2017, 12:51:28 PM »

Roger that - after doing a little reading on BG's page and others I'll find a way to do a clean install straight to the battery.

Thanks - we can now close this thread.
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SOFAR
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« Reply #3 on: January 02, 2017, 01:01:27 PM »

I'm sure the thread will resolve itself.. Eventually
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AA4PB
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« Reply #4 on: January 02, 2017, 01:14:57 PM »

Bear in mind that a radio like the 7900 draws maybe 12-15 amps in transmit. 

According to the manual, worst case is 9A, Tx 45W on 430MHz
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Bob  AA4PB
Garrisonville, VA
W8JX
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Posts: 13268




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« Reply #5 on: January 02, 2017, 02:30:13 PM »

Bear in mind that a radio like the 7900 draws maybe 12-15 amps in transmit.  
Best bet is direct battery connection with fuses close as possible to the battery end.
Whatever you do DO NOT use the "power socket".  
Regardless of how well it is fused, the connection is good for maybe 7 amps.  

73
WB2EOD


Bear in mind that rig does not draw that much power and some accessories draw far more power than that radio. (amp rating for rigs are worst case scenario with 15% over voltage too and not real world but many that quote amp draw for specs as the gospel and do not understand this some even pull numbers out of thin air) Add a fuse will work fine here just make sure you get polarity right so fuses are not in series. Some make off the wall predictions that have no merit or factual basis. The spades can handle a lot more than 7 amps as witnessed by some use 20 amp and bigger fuses. Plus I want to add that many cars are series fused meaning that they have main distribution fuses that then feed busses that are fused for other devices so you cannot over draw buss capacity.
« Last Edit: January 02, 2017, 02:34:33 PM by W8JX » Logged

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Ham since 1969....  Old School 20wpm REAL Extra Class..
AI7PM
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« Reply #6 on: January 02, 2017, 05:34:35 PM »

She loves the car and is very resistant to me out there drilling a hole in the firewall or cutting the existing grommets on factory wiring harnesses that go through the firewall,

Tell her she can't use the vacuum cleaner anymore, because holes had to be cut in the drywall for electric outlets.
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W8JX
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« Reply #7 on: January 03, 2017, 06:05:12 AM »

I should add to this subject of add on circuits that I have a old 97 Saturn that started having intermittent power distribution problems over a year ago. It would cause loss of power to fuel pump and ignition circuit in car and it would not start. When I attempted to troubleshoot and fix problem it was impossible to remove a fuse panel in question in car to gain access to rear of it to find problem with tearing dash and center counsel apart. I "fixed" it by running a 10 ga wire from 30 amp fuse for it in main distribution panel under hood to panel in question and then pig-tailed two spade connectors on 16 ga wire together that was feed from 12 ga wire. (BTW single wire current ratings are a lot higher than when bundled) I then inserted the two spades in two places in fuse sockets next to fuses on hot side on buss that was loosing power. Been over a year now and I have had zero problems with fix and car is driven daily by XYL to work in winter and is very reliable as it always starts in any temperature and has a great heater (which is why XYL likes it in winter because it will roast even well below zero and is good on slick roads and it keeps newer car out of salt too) It has 210k miles on it now. I will have to replace it one day but I know its quirks and is pretty low tech and easy to fix/trouble shoot. (Saturns then used a German built Opel engine and a high quality Asain automatic tranny made in Japan)
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Ham since 1969....  Old School 20wpm REAL Extra Class..
K1DA
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« Reply #8 on: January 07, 2017, 11:24:26 AM »

I use an FT  7800 with a LIDO flex shaft mount  for the head.  Many Camrys have a fuse box in the passenger compartment,  by the driver's left knee. Mine has a lot of empty slots for uninstalled  accessories such as heated mirrors and the like.  Most slots are for at least 10 amps (marked on the box cover) and I found several  for 20.  Works fine, no noise on the DC.  Be sure the hot side of the tap is inserted in the hot side of the fuse slot in the car.
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W8JX
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« Reply #9 on: January 07, 2017, 07:31:40 PM »

I use an FT  7800 with a LIDO flex shaft mount  for the head.  Many Camrys have a fuse box in the passenger compartment,  by the driver's left knee. Mine has a lot of empty slots for uninstalled  accessories such as heated mirrors and the like.  Most slots are for at least 10 amps (marked on the box cover) and I found several  for 20.  Works fine, no noise on the DC.  Be sure the hot side of the tap is inserted in the hot side of the fuse slot in the car.

All fuse "sockets" have same power capacity because they are all feed from a common buss bar on back. And that buss is protected by a buss feed fuse. While some sockets may be marked 5, 10 or 20 amps, the hot or feed side of them all have same capacity,
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Ham since 1969....  Old School 20wpm REAL Extra Class..
AD5TD
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« Reply #10 on: January 09, 2017, 08:39:10 AM »

FWIW: I have my FT-8800 running from an "ad a fuse" on my "power port" in my truck.  I have had NO issues running it full power.
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