Question on installing Dual CB Antennas

[K_Arts]

Ok guys... I need some of your expertise.



I'm almost ready to get a CB in my truck... though here's my Delima. I want to install Dual Antenna's when I do it.



Currently I am learning all about how Antennas transmit in school. I know all of the equations on how to measure the wavelength of the antenna, pending on what frequency I am broadcasting. Though when you install 2 antennas together it can create problems.



Each antenna has certain electrical characteristics, so when you add dual's your second antenna will either get the traits of being a reflector antenna or a director antenna. In case you are not familiar with the terminology, using the antenna as a reflector, the antenna will resonate at the same frequency as the first antenna and help your broadcasting range, where using a Director antenna, they antennas will resonate at a different frequency causing them to broadcast only in a certain direction.



What is the equasion to figure out what the distance needs to be between the two antennas to use the second antenna as a Reflector antenna??



I hope this makes sense... if not, I'll post up more information as to what I mean.



Thanks



Kev

 

[steve2118]

antennas need to be one wave lengh apart to work properly

 

[baby.driver]

I think that's 1/4 wave apart.



Jay

 

[SteveE]

Antenna

Try a center mag mount. I think that duals have to be 1 wave length apart and thay can't be swaying and bending back like they do at 65 mph.

try www.qrz.com for links for antenna information. It's for ham but the info is there for anyone.

w7sje

hope that helps

 

[Bigstick]

THe correct measurement is actually 60" apart I used to have duals with one dummy on old truck but now on this one I have a MAXRAD antenna it looks almost dead on the radio antennat just a little taller and I made a custom bracket that mounts between the hood and the fender out of SS. I can send pics if ya like.

 

[jtisdale]

simple

Install both as desired, but only hook up one. No one will even notice that only one is hooked-up. Just my $. 02

 

[K_Arts]

Thanks for the replies guys.



I know that the antenna needs to be 1/4 wavelength, but I just can't find the exact equasion that I'm looking for. .



The main reason that I'm looking for the equastion is that the mounts that I have seen for Duals, vary in the distance apart so I'm not sure which one to get.



Thanks



Kev

 

[Silver Streak]

ANT. MOUNT

I use a wilson 1000 mag. mount, it works great and gets a good match and you do not have to drill any holes. good luck



SILVER STREAK

 

[Old Man]

Dual CB Antennas

Go to Firestick. Com. They have got a ton of information on their website, also talk to Rick Sr. , he answered all of my questions. Their coax wire for duals (mini) is first class. At present I am running duals mounted on the side of the tool box with a uniden grant lt. My swr's are running 1. 7. They recommend running 4 ft. antennas. Just trying to help.

 

[EScott]

Assuming that you want the antenna system set up for the middle of the band ie channel 20:



1/2 wavelength is

468/freq or 468/27. 205= 17' 2. 432"



1/4 wavelength is

234/freq or 234/27. 205= 8' 7. 216"



I don't have any of my books handy, but if memory serves me correctly in order to get the majority of the signal to radiate to the front and rear of the array you have to use the 1/2 wavelength spacing, which is obviously going to be tough to do on a truck.



If you really want to use phased verticals just make sure that the leads between the antennas are cut as closely as possible to the same lengh. You will also need to avoid making the cables resonant, ie anywhere between 17' and 17' 6" long. The best bet is to measure, and custom cut them because having a big wad of extra cable doesn't help either.



It's been my experience that dual CB whips actually radiate less, than a well installed single. They look cool, but that's about it.



Erin