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Old 08-18-2015, 08:01 PM
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Default Dual CB antennas.

Searched, sort of, couldn't find anyone talking about it in here.

So anyways, I see them often. But are they a good idea? Bad idea?
What are the advantages?

And... Go!
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Old 08-18-2015, 08:03 PM
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Thought that was only for semi's
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Old 08-18-2015, 09:44 PM
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There is no practical advantage. You can in theory add directionality but getting the phasing right isn't trivial and more trouble than it's worth.
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Old 08-18-2015, 10:16 PM
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So it's basically for show, and that's about it?
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Old 08-18-2015, 10:31 PM
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One antenna is way more effective than two. I believe having two connected can actually reduce your power... Unless you have some crazy amplifier before the splitter?

I've always thought it was for show.
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Old 08-18-2015, 10:40 PM
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Ok. Fantastic.

Thanks, guys.
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Old 08-18-2015, 11:30 PM
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I thought that the second antenna wasn't even hooked up on many semis - it's just for show.
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Old 08-19-2015, 06:19 AM
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Quote:
Originally Posted by aprosise View Post
One antenna is way more effective than two. I believe having two connected can actually reduce your power... Unless you have some crazy amplifier before the splitter?
The number of elements doesn't change your power but if done properly will change the radiated pattern. If done incorrectly the elements will interfere, reducing your effective radiated power and potentially ruin your radio. The term is phased antenna array.

http://lmgtfy.com/?q=phased+array+antenna

Phasing is fundamental to radar and it's fairly common with commercial broadcast antennas. Hams sometimes use phased arrays, one common configuration being a quad with 4 elements. Also Yagi antennas rely on element phasing to work. Array phasing is the basis for beam shaping that allows DirecTV to transmit Denver stations and not Houston or Chicago to you. But suffice to say, it's more than just hooking up two whips and letting 'er rip. The elements are tuned differently, the distance between the elements and the feed line lengths are critical.
Quote:
I've always thought it was for show.
Would make sense.

However, the distance between the two whips would need to be some multiple of the wavelength. If a truck is exactly 8 feet wide that would be 1/4 wavelength at 11m, so it's theoretically possible to phase them. But with them flopping around in the wind it becomes nearly impossible to keep them phased, which is why it's not practical for mobile use like this.
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Old 08-19-2015, 08:19 AM
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My understanding it's the distance needed between them is not easy to achieve on anything but a semi. Then everything Dave said.

I have duals on my truck using Gamiviti hood mounts but one is CB other is HAM.
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Old 08-19-2015, 10:11 AM
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on semis both antennas are hooked up, not just for show. but to work properly, they need to be approx 8' apart.

duals really aren't used much anymore, cbs are slowly going the way of the dodo, but for those running them now, they run multiband antennas, so the radio and cb are both on one antenna.
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