wiring for car-battery, fuse block, etc.

[scottyhetzel]

On the order of fusing, which is "better", a circuit breaker or a fuse at the battery.

I've been told that a circuit breaker does not "like" the heat of an engine compartment where a fuse is
more "tolerant".

Ron

Resetable breakers use heat as their current limit . So 200 degree engine de rate the breaker. So in theory you need to up the breaker size. Fuses generally have higher per resistance ... plus breakers can reset when trouble is cleared...just don't use auto reset... you manual reset like copper products .

 

[ramal121]

I will echo Rred's comment on circuit breakers welding themselves together, however I have only seen this with auto reset breakers. The marine kind that have the trip/disconnect lever will always separate the contacts even if they are sticking. But if they are at that point in their lives, they will trip early due to heating caused by contact resistance. This is beyond the de-rating scottyhetzel mentioned by installing them in a hot engine compartment.

Normally a fuse is safe in automotive applications, but in multi bank battery bank applications (say solar), even a standard automotive fuse will draw an arc when it blows and something will melt somewhere somehow. In this instance only a self quenching fuse like a class t series should be used.

 

[Delivers1234]

Hi all. So I'm still gathering materials for my equinox. Silk comm. will install the 2 nmo mounts and 1 CB antenna. They could not get a hold of a 2m/70cm antenna. I can go to ham radio outlet. In terms of roof placement I think the CB ant. Will go in the center. Where would the 2m/70cm ant. go? I'm asking so I can understand when silk adds the 2nd nmo mount. They said I could bring one an ant. And they would add it on.

 

[mmckenna]

There's two things you need to be concerned about:
1. antenna spacing
2. proper ground plane.

Antenna spacing is necessary to provide enough separation between the transmitting radio and the other radio receiver. If the two antennas are too close together you can induce a lot of RF energy into the other radio. This can easily damage the receiver.
Ideally you want at least 1/4 wavelength, more if possible.
Issue is, that will be impossible to get than on CB frequencies, where 1/4 wavelength is 108 inches. Good thing is that the CB is only running 4 watts maximum, and less by the time it makes it to the antenna.
The problem is with the amateur radio. It's running 50 watts, and that could damage the CB receiver. Good news is that 1/4 wave on 2 meters is 19 inches and 1/4 wave on 70 centimeters is about 6 inches.

So, you'd want at least 19 inches between the two antennas, more if you can do it.

But, you want a good ground plane under the antenna. Ideally, 1/4 wavelength in all directions.
Not an issue for 2 m or 70 cm where you only need 19 inches (or 6). That's pretty easy to do on an SUV.
CB would need the 108 inches, but there is no way to achieve that on your vehicle, so just do the best you can.

If you've got a sun roof, it's going to be harder. If you don't, it's pretty easy.

I'd put your amateur antenna in the better location, center of the roof, and move the CB towards the rear. That should work out well.

Silke should do a good job.

 

[Rred]

I'm thinking that in order to get more space between the antennas, you'll have to do some compromising on placement. Perhaps mounting the two NMO mounts for the ham radios inwards of the "B" pillars, close to the edges of the roof. The B pillars will be solid metal, acting like radials or a good counterpoise. Or perhaps halfway between the A and B pillars, again, close enough so either of them are functioning as great counterpoises.

Then move the CB antenna to the middle of the roof, as close to the rear as you can. This will degrade the performance behind you, but optimize it in front of you, and usually that's where you "need" the CB to connect with most.

You've GOT to degrade the performance of all the antennas, in order to get the most separation and protection that you can against overloads from one to the other. The shop should have some good input on how far you can push that, and where the antenna mounts can actually go, since roof supports, etc. will dictate some of that.

Then if they can snake all the cables down one pillar, to come out in whatever location (A pillar for dash, B pillar or C pillar for rear seat) you plan to put the radios nearest to.

One great thing about NMO mounts is that any NMO antenna whip simply screws on. As long as they have installed the mount, all you have to do is pick up any NMO antenna and screw it on. Preferably with a little contact grease and enough torque to make sure it stays put.

Easy enough to find a good 2m/70cm combi antenna from internet sources, and you can have a brand name in your hands in under a week that way. FWIW, anything with an exposed helical loading coil or other "stuff" on the whip is likely to whistle in the wind. I'd expect any of the brand names (Diamond, Comet, Larsen, etc.) to perform well enough, even if each performs "differently" in some way from the others.

 

[SteveC0625]

One final thought....

If you are installing multiple NMO mounts on the roof, label each coax at the connector end so you'll know which is which. That way, you can shuffle antennas around and connect them to the matching radio.

 

[Delivers1234]

One final thought....

If you are installing multiple NMO mounts on the roof, label each coax at the connector end so you'll know which is which. That way, you can shuffle antennas around and connect them to the matching radio.

I'm headed to San Jose to ham radio outlet. Any recommendations for a 2m/70cm?

 

[prcguy]

Larsen NMO2/70B.
prcguy

I'm headed to San Jose to ham radio outlet. Any recommendations for a 2m/70cm?

 

[mmckenna]

I'm headed to San Jose to ham radio outlet. Any recommendations for a 2m/70cm?

NMO-2/70. Accept no substitutes, no matter what the guy behind the counter says. Avoid the amateur/consumer grade antennas. They may save you a few bucks, but you'll be disappointed in the long run.

Usually I agree with what PRC recommends, but in this case I'd avoid the NMO-2/70B. The "B" model is the black whip. They really do look great, especially on your white vehicle. It'll look great probably until mid-July. After a few trips up and down Highway 101 you'll hit enough bugs that the powder coating will start chipping off. Underneath will be shiny metal. After a year or two, there will be a lot of shiny spots. You can touch them up with a Sharpie pen, or some black model paint, but it'll just keep happening.
You might be OK with that, especially if you like the looks of the black whip. I'd understand...

After trying one of the black whip antennas from Larsen, I stopped buying them and just stuck with the "C" models, which are the chrome whips. They'll look great for years.

If you do really want the black whip model, it'll work fine. The black sharpie trick works for a while, but needs frequent touch ups. Black paint works a bit better. On the shorter 1/4 wave whips, I've used black heat shrink tubing with good results. Wiping it down with Armor All now and then keeps it shiny. Problem is the NMO-2/70 is a long antenna and the heat shrink trick doesn't work so well.

Either way, the Larsen NMO-2/70 (B or C) is what you want. Don't be tempted by the flashy off brand antennas, stick with the original.

While you are there, you might want to check into the Larsen NMO-27, if you don't already have one. That's the CB coil/whip. Having the matched set will look great.
Last time I was up at that HRO, they had both in stock.

While you are there, pick up a sandwich at the Togo's across the parking lot.

 

[AK9R]

My experience with the NMO2/70B is different. I have found that the black coating holds up pretty well as long as the antenna doesn't have mechanical contact with anything hard, like the bottom of a garage door.

 

[mmckenna]

My experience with the NMO2/70B is different. I have found that the black coating holds up pretty well as long as the antenna doesn't have mechanical contact with anything hard, like the bottom of a garage door.

Yeah, it's a pretty good coating. I've had issues with bugs hitting it at highway speed, probably some gravel/hail/tree branch damage along the way, too.

 

[cmdrwill]

Yeah, it's a pretty good coating. I've had issues with bugs hitting it at highway speed, probably some gravel/hail/tree branch damage along the way, too.

They have some really nasty bugs in that part of California.

I do admit black antennas look much better and do not seem to be as easy to 'spot'.

The most important thing in all this: Get a quality commercial brand, avoiding the knock offs and imitations.

 

[Project25_MASTR]

Yeah, it's a pretty good coating. I've had issues with bugs hitting it at highway speed, probably some gravel/hail/tree branch damage along the way, too.

I've had a Larsen NMO27B and a NMOQB on my XJ for nearly 4 years now…even where they contact the garage when I park it there is no marring of the finish. Now, that Jeep stays primarily in Colorado and only gets driven 5k miles a year but when it's out…it's not nice out nor is that vehicle a pavement princess (compared to my pickup). Last time I was driving it in Texas I got caught up in a hail shaft which broke the windshield, put golf ball sized dents in the roof, smashed out a light bar…no damage to the Larsen's though.

Had a NMOQB and NMO50B on my Trailblazer for a good 30,000 miles…same results as with the XJ. The NMOQB was permanently bent when a hail stone struck it…didn't damage the finish.

Overall, I've never had an issue with the black finishes. However, mileages do vary as do conditions so what I may experience are certainly just a part in the bigger picture of how these products actually weather.

 

[mmckenna]

That's good to hear. Maybe I need to give them another try. My NMO-27 from about 20 years ago was the one that had the issue. Hopefully they found a better way to do the coating.

Thanks for the info.

 

[Project25_MASTR]

That's good to hear. Maybe I need to give them another try. My NMO-27 from about 20 years ago was the one that had the issue. Hopefully they found a better way to do the coating.

Thanks for the info.

Currently it is plastic based and not powder coat based like what the (generic) older black whips used to be.

 

[mmckenna]

Currently it is plastic based and not powder coat based like what the (generic) older black whips used to be.

Hmm, I've got a white truck, and the black whips do look good on there. I'll have to give one a try.

Since I learned something new today, can I take the rest of the day off?

 

[Delivers1234]

Hmm, I've got a white truck, and the black whips do look good on there. I'll have to give one a try.



Since I learned something new today, can I take the rest of the day off?

Ok. Who wants to help me Sunday?
Salinas CA

 

[12dbsinad]

Hmm, I've got a white truck, and the black whips do look good on there. I'll have to give one a try.

Since I learned something new today, can I take the rest of the day off?

I've also have had no issues with Larsen black whips, and I use them where calcium chloride in the winter rots your vehicle out in 3 years... literally.

Give the newer ones a try for sure.

 

[mmckenna]

Ok. Who wants to help me Sunday?
Salinas CA

I'm booked, but whatcha need?

 

[Delivers1234]

I'm booked, but whatcha need?

Got the Larson! Nice. I'm ready to wire but worried about doing it without help. I'll see how it goes.