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Old 05-29-2009, 09:13 AM
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Default antenna- big antenna or big ground plane?

I've been having this debate with myself, and keep losing. What would perform better- a 38" antenna clipped to the edge of a fender, or a 12" antenna smack dab in the middle of a roof? Everything else (2m/70cm ant., band, power, etc.) remaining constant... yeah I'm thinking about drilling a hole again.
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Old 05-29-2009, 09:37 AM
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I had this discussion (sort of) with the dude at HRO when I was buying my Ham and antenna. High and center of the roof can't be beat according to him. I opted for a long antenna that folds and used a magnet mount base. I can attach it to center of the roof on Hilux or FJ60, and also use it on the flat top surface of the FJ40 fender.
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Old 05-29-2009, 10:27 AM
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Default 38" antenna in the center of the roof...

The comparison is a little skewed. The stubby looses so much because of its size and needing to have a loading coil to compensate for the length. By this, the 38" antenna (IMO) would far surpass the stubby, no matter where you put either. Not saying that the 38" one doesn't need a loading coil, it very well may (and probably does). The losses inherent in the antenna system caused by said coils are far more on the stubby than on the 38".

Keep in mind, too, that placement is critical for a vertical for its omni-directional capabilities, no matter what length. A long antenna on the bumper in the front might have problems reaching things whose signal comes from the direction of the rear of the vehicle, etc, whereas the stubby might appear to have superior range on the roof in all directions.

Crown and Cola. Just do it.
Cut a hole in the roof, just do it.
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Old 05-29-2009, 10:38 AM
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Ok so you're saying Comet SBB-5 clipped to the fender, or even bolted to an ARB, is going to out-perform a Comet SBB-1 mounted in the center of the roof?
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Old 05-29-2009, 11:09 AM
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Quote:
Originally Posted by nakman View Post
Ok so you're saying Comet SBB-5 clipped to the fender, or even bolted to an ARB, is going to out-perform a Comet SBB-1 mounted in the center of the roof?
Yes and no. But in general, no. The 1/4 wavelength (SBB-1) put in the middle of the roof will perform well, be truly omnidirectional. The SBB-5 (or similarly a 1/2, 5/8, multiple band, etc.) will out perform the little guy when you're on the fringe because it's slightly more directional and has more radiating length. But put in an non-ideal spot you will pretty much negate the advantages that the longer antenna will provide. So if you can live with the shorter antenna on your roof (and I appreciate that it's a PITA with garages), the middle of the roof is really noticeably better. Honestly between the NMO2/70 (long dual band) and the NMO2/70SH (stubby dual band), there's not much difference in the real world around town. I do get a bit more range on simplex, but it's also noticeably more sensitive to direction (i.e. more fade as the antenna flops around in the wind). Repeater-wise, no difference really.
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Old 05-29-2009, 11:17 AM
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If I can negotiate the garage entry, then I'm really leaning towards the short stubby route smack dab in the center of the roof. Then when I head out on a trip I could always swap antennas to a larger one, then I'm in an even better situation... only catch is they'd all have to have the same mount, like NMO.

Is there a better, or even shorter option for a short stubby than the SBB-1? I only am leaning that way because I already have one..
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Old 05-29-2009, 11:29 AM
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Originally Posted by nakman View Post
If I can negotiate the garage entry, then I'm really leaning towards the short stubby route smack dab in the center of the roof. Then when I head out on a trip I could always swap antennas to a larger one, then I'm in an even better situation... only catch is they'd all have to have the same mount, like NMO.

Is there a better, or even shorter option for a short stubby than the SBB-1? I only am leaning that way because I already have one..
Yup, pretty much right. Center of the roof is always preferred and with the NMO you can swap back and forth. There might be better antennas or not, but no matter, just run whatcha got now (at least if it's NMO).
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Old 05-29-2009, 12:25 PM
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This is just my opinion, so take it for what it's worth...

I don't like putting the antenna on the roof because it makes it even more prone to hitting trees on the trail -- especially if you're running a stiffer short antenna which will break rather than bend.

If you mount it to the fender, you'll get plenty of good performance, and the antenna will be less likely to smack stuff on the trail and driving around town.

Yeah, I run the 5/8 wavelength Larsen on the back top corner of my 80 on the trail, but it's extremely flexy -- it's just a piece of wire. A new whip costs $13. And I just bought a shorter version that I'm going to run around town.
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Old 07-26-2009, 07:25 AM
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Interesting query... best rule of thumb is that the shorter (1/4 wave antenna) would work best in very hilly areas, and the longer one (5/8 wave antenna) would be best when used in flatter terrain. I use the 1/4 wave antennas here in Estes Park with great results and when I go to the flatter areas, I switch to the 5/8 wave one. Most of the time the 5/8 will be the best choice as an "all-use" antenna because the 1/4 wave falls short in performance in the flatlands, and the 5/8 wave does work well in the hilly areas. Hope this helps. Cheers, Bob kc0kbp
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Old 07-26-2009, 10:56 PM
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After this weekend I'm done with the lip mount on the top of the rear hatch- that thing found every single tree branch even with the short antenna. I've already lost one good antenna to that mount position too... if my antenna were closer to the center of the truck it would have been in the clear most of the time, as all the branches seemed to be towards the sides. I think I'm going back to the side of the fender up front, where I can drive in the garage without having to remove it. double bonus
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