Wiring power for ham? (1 Viewer)

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Hi guys,

I got the Yaesu 7800r, k400c mount and sbb1 antenna ready to install here. The main question I have at this point is how to wire the power supply. I read a lot of people wiring the auxiliary fuse box, but I'm not sure how to tackle this. Any tips?

Here's a pic I stole from someone else's install, maybe you can point out what I need to know.
Yaesu_Install-2.jpg
 
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Wire direct to the battery with fuses as near the battery as possible. That's the recommendation that Yaesu gives for their rigs to minimize noise pickup and to provide the lowest voltage drop between the battery and the rig. Just check their manual on how to wire up the rig in a mobile environment.

Run BOTH Ground and Positive wires from the battery to the rig. Put fuses in line from the battery right near the battery to protect the wiring in case of shorts.

I'm just finishing up installing a Yaesu FT857D in my 80 and I have 10 gauge wiring from the battery to the rig. The rig is installed in the rear USPS cubby with power cable running in a jacketed sheath from the battery through the firewall, under the carpet along the doors up into the rear arch area. I've also provided a direct ground connection between the rig and the body of the vehicle near where the rig is installed.

cheers,
george.
 

e9999

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I'm running my 7800 off the cig lighter, admittedly a temporary-looking setup. I looked at the radio and circuit specs and it should be fine. No fuse blowing so far at high power setting.
 
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Firstly - running of the cig lighter is not a good choice - the Yaesu manual is pretty specific about how to wire power up, but hey - what do they know...

Regarding the FT857D, I bought a Little Tarheel antenna. I'll start a new thread and detail the install (after the fact) in the next week or so.

I have the VHF/UHF stuff working - since it just inherited the antenna and wiring from the FT1802 install. I now need to hook up the manual screwdriver controller and see about getting the HF antenna tuned to a band and testing it out - I'll probably try 6M first as a sanity check with my vx7r. Then I'll try the HF bands - definitely a lot for ME to learn yet.

cheers,
george.
 
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Ok, I got everything wired up and made my first three contacts this afternoon. A guy in Santa Barbara, a guy on a cruise ship off Catalina Island and another guy in Glendale. This was off a repeater on Catalina Island about 50-60 miles away. I hit that with 5w! The contact in Santa Barbara said I had a little signal weakness to I pumped it up to 50w (I think, I just set it on High) and everyone said the signal was strong and clear.


Quick question though, when I started the truck up I definitely heard some noise coming off the speakers that I didnt have while the truck wasnt running. I wired directly off the battery, isnt wiring off the battery supposed to eliminate the noise? Anyway, still very happy with it. Now I just need to figure out how to mount the faceplate and mic in a nice clean fashion.
 
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Yeah, you'll still have some noise - alternator, ecu etc etc. You can adjust the squelch to cut out the background noise when the vehicle is running.

cheers,
george.
 
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Here's a pic I stole from someone else's install, maybe you can point out what I need to know.

George has given you good information and I agree with him that using a lighter plug for a high power transceiver is bad advice.

I'm pretty sure that is a pic from my install. That 2nd fuse panel is located on the passenger side and it has a single 4ga (IIRC) wire going to the second battery location, but it is physically attached to the primary battery. There is another fuse at the battery on the 4ga wire. Grounding is at the main ground point under the center console. I chose not to run pos & neg 12v wire directly to the battery.

An excellent source of information on how to minimize ignition noise is here: Ignition Notes on RFI. FYI, that site is well known as one of the best sources for information on mobile installs.

George,
You mention that you are installing the new 857 in the rear cubby. From your description, it doesn't sound like you ran separate pos & neg wires to the battery. Am I reading this correctly?

-B-
 
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e9999

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George has given you good information and I agree with him that using a lighter plug for a high power transceiver is bad advice.

snip

-B-



would you please elaborate?
 
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would you please elaborate?

Do you want me to elaborate on why I agree with George or do you want me to elaborate on his point that it is a bad choice?

Elaborating on the latter... Wiring & Grounding

Excerpt:

"The most important consideration is where the power comes from. You should never power any amateur radio from any existing vehicle wiring harness, QRP or otherwise. This includes accessory (cigarette lighter) sockets, and using a modified blade fuses as power taps. If you violate these basic rules, you run a great risk of burning the vehicle’s wiring harness which might start a fire. There is absolutely no auto repair more costly than an electrical fire!"

-B-
 
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George,
You mention that you are installing the new 857 in the rear cubby. From your description, it doesn't sound like you ran separate pos & neg wires to the battery. Am I reading this correctly?

-B-

Definitely Power and Ground 10 gauge runs direct from the rig to the aux battery and fused in the battery area. I also grounded the rig to the body near the cubby. Yaesu recommends grounding the rig local to the install in addition to separate power/ground runs to the battery.

cheers,
george.
 
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I'm still amazed that I was able to talk to someone 100 miles away in Big Bear while sitting in my parking space in LA. This is a cool 'mod'
 

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Do you want me to elaborate on why I agree with George or do you want me to elaborate on his point that it is a bad choice?

Elaborating on the latter... Wiring & Grounding

Excerpt:

"The most important consideration is where the power comes from. You should never power any amateur radio from any existing vehicle wiring harness, QRP or otherwise. This includes accessory (cigarette lighter) sockets, and using a modified blade fuses as power taps. If you violate these basic rules, you run a great risk of burning the vehicle’s wiring harness which might start a fire. There is absolutely no auto repair more costly than an electrical fire!"

-B-


the danger of powering a radio from existing harness may or may not be true for a particular install, but the "great risk of burning..." is certainly not true as a general statement and way overgeneralized, IMHO. It is entirely a function of the current drawn by the device. If the current is less than the capacity of the lighter wiring and fuse, it should be no problem at all to connect to that outlet and no different than connecting directly to the battery. It is entirely a matter of whether you know what you are doing or not. Pontificating statements as in the excerpt you used, are just that. Although I'll grant you that it suggests probably a safest route to take for unknowledgeable people.

As to that circuit being a bad choice for noise issues, that is a different story altogether. But again, mine sounds just fine.

Reread my original post, please. That was just a statement, not even a recommendation.


And I always welcome evidence that I'm mistaken and should reconsider my erroneous ways... :)
 
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the danger of powering a radio from existing harness may or may not be true for a particular install, but the "great risk of burning..." is certainly not true as a general statement and way overgeneralized, IMHO. It is entirely a function of the current drawn by the device. If the current is less than the capacity of the lighter wiring and fuse, it should be no problem at all to connect to that outlet and no different than connecting directly to the battery. It is entirely a matter of whether you know what you are doing or not. Pontificating statements as in the quote, are just that. Although I'll grant you that it suggests probably a safest route to take for unknowledgeable people.

As to that circuit being a bad choice for noise issues, that is a different story altogether. But again, mine sounds just fine.

Reread my original post, please. That was just a statement, not even a recommendation.

avatar1786_3.gif


Everything I have read says hook directly to the battery

:cheers:
 

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avatar1786_3.gif


Everything I have read says hook directly to the battery

:cheers:




ooooh, OK, if Deltalina says so, then I'm ready to fold... Can't resist her... :D







Anyways, regardless of all the discussion above, always do the safest thing for your situation, of course... :)
 
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One last comment before the dead horse icon needs to be used...

Just because something appears to work doesn't mean that it is the right way to do things - ESPECIALLY if you don't understand the design of the equipment (at the circuit level).

Lower input voltage (especially in many modern pieces of electronic equipment that use switching supplies in various parts of the design) mean that input currents have to be higher to generate the same output power. Manufacturers, e.g. Yaesu, specify minimum input voltage (an max of course) to ensure that input currents are within spec for the operating mode. Most of the rigs will limit output power if the input voltage is too low to prevent damage.

Obviously the real issue is during transmit when high current is being drawn - when you can't hear if your signal is cr@p. A cigarette lighter is a rather pathetic power connector and to rely on it to provide stable power to high power electronic equipment is not a particularly good choice. Voltage losses across smaller gauge wiring in addition to poor connections (higher resistance) all mean lower and possibly out of spec voltage reaching the rig during transmission.

Running lower input voltages can often mean higher input currents that can stress electronic components. Efficiency is also lower leading to higher heat dissipation in many of the active devices that is never a good thing.

Finally, I use 40% efficiency as my seat of the pants figure for transmission power versus input power. i.e. if you have 50W output I assume at least 125W at the input. That means around 10A during transmit. Just 0.1ohms of resistance along the entire battery to rig wiring means 10 x 0.1 = 1V voltage drop.

My >2c as an electronics engineer that still actively designs rather than manage...

cheers,
george.
 

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no doubt there can be electronic issues due to voltage drop, noise etc. But saying that you're likely to start a fire because of using the lighter plug is a bit of a stretch for a 50W radio, IMHO...

over and out on this issue... :)


added later on: OK, never mind that last one, I'll add one more thing. I did go and check the voltage drop on mine since this is an interesting issue and George knows his stuff. At highest power (antenna inside the truck not sure what difference that makes), I measured 12.7V at the fuse downstream of the lighter plug when the battery terminals were about 14.3V or so (engine running). That's about 1.6V drop at 10+ A (I did try to measure the current but my meter tops off at 10A and it was OL). More than I expected. Maybe the cheap plug? So, indeed, with the engine off, it could well give you only 11V (WAG). Now the 7800 specs say 13.8V +/- 15%, so that implies 11.7V min. Not sure if that's a real lower limit. But indeed the supply may well be too low with engine not running. No biggie, I can run the radio directly off my jumper battery if the engine is out, but still good to know. Now, of course, there would be a drop with direct connection to the battery as well, but that should be much lower. 12 ga is something like 0.02 ohms for 10 ft.
Still not too worried about fire, though... :)
 
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ginericLC

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I plugged mine into my cig lighter in my 100 when I first got it. As soon as I went to high power it blue the fuse. I believe it was a 40 AMP fuse. I wired it direct and I don't have any problems now.
 
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no doubt there can be electronic issues due to voltage drop, noise etc. But saying that you're likely to start a fire because of using the lighter plug is a bit of a stretch for a 50W radio, IMHO...

over and out on this issue... :)


added later on: OK, never mind that last one, I'll add one more thing. I did go and check the voltage drop on mine since this is an interesting issue and George knows his stuff. At highest power (antenna inside the truck not sure what difference that makes), I measured 12.7V at the fuse downstream of the lighter plug when the battery terminals were about 14.3V or so (engine running). That's about 1.6V drop at 10+ A (I did try to measure the current but my meter tops off at 10A and it was OL). More than I expected. Maybe the cheap plug? So, indeed, with the engine off, it could well give you only 11V (WAG). Now the 7800 specs say 13.8V +/- 15%, so that implies 11.7V min. Not sure if that's a real lower limit. But indeed the supply may well be too low with engine not running. No biggie, I can run the radio directly off my jumper battery if the engine is out, but still good to know. Now, of course, there would be a drop with direct connection to the battery as well, but that should be much lower. 12 ga is something like 0.02 ohms for 10 ft.
Still not too worried about fire, though... :)
Wiring direct to the battery also acts as a noise filter. Your battery acts like a capacitor and filters some of the induced noise produced by all the electro mechanical devices under the hood.

Additionally under high power (amps) you want a good solid connection. Not something as potentially intermittant as a Cig connection.

De N6KML
 

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I plugged mine into my cig lighter in my 100 when I first got it. As soon as I went to high power it blue the fuse. I believe it was a 40 AMP fuse. I wired it direct and I don't have any problems now.

wow! 40A? That is 500+W! Where did all that power go?
 

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