Dual antennas or single?

To the sides of both antennas. Front to back of your truck. It's better to run one more omni directional.

 

but don't you need alot of space between them and they have to be in line with each other? I am thinking about biting the bullet on two 10k but I will have to angle them far forward to get them below the tree lines.

 

This was helpful to me in my understanding. I am new to this BBS so I didn't know how to just use thanks, sorry. Also tried to PM you, but got a msg that I didn't have enough posts to do that. If you have any suggestions for online info like this related to mobile installations, please post them.
Thanks In Advance

 

This was helpful to me in my understanding. I am new to this BBS so I didn't know how to just use thanks, sorry. Also tried to PM you, but got a msg that I didn't have enough posts to do that. If you have any suggestions for online info like this related to mobile installations, please post them.
Thanks In Advance

 

OK, here is the link we all need to properly understand the basics of antenna cophasing in MOBILE applications, such as is the TOPIC of this POLL. If you are already a licensed HAM, and you are using this TRUCKERS CB FORUM, and you do not DRIVE A TRUCK, but you still wish to discuss 11m antenna theory with TRUCK DRIVERS intelligently, this link is a MUST READ link for ya! (DrumRoll Please!)
http://signalengineering.com/ultimate/mobile_antennas.html

OK, now that you have read this info does everybody understand that the advantage of using twin antennas on our vehicles is OMNIDIRECTIONAL efficiency of our RF output? Is there a HAM in the house that can honestly STILL claim that he/she/it finds MOBILE ANTENNA THEORY complicated? Is there anybody left here at this poll that does not know the CORRECT answer to the poll above? OK HERE IT IS:

Co-Phasing Your Mobile Antennas ("Twin Truckers")
Co-Phasing antennas simply means taking two identical antennas, mounting them on the vehicle and feeding them in-phase. One of the biggest misconception of radio operators is what kind of effect this has on the radiation pattern. Most people think that after you Co-Phase two mobile antennas, your signal will be strongest in line with the vehicle body (meaning the signal is strongest down the road straight in front of you and straight behind you also. This is the theoretical effect that you would get from co-phasing two omnidirectional antennas. However, to realize this effect you need to satisfy a couple of requirements. For one, a good earth ground with long (over a wavelength or so) radial wires is required. Secondly, at CB frequencies the closest you would be able to place these antennas are about 18 feet apart. Since it is impossible to satisfy these requirements, the effect of co-phasing is seriously diminished. Unfortunately, even the "Radio Shack Antenna Book" states that co-phasing two mobile antennas will produce a two directional signal.
So then, is there any advantage to co-phasing two mobile antennas? Why yes, there is. Before we noted that the radiation pattern of a single antenna is "pulled" where there is the most metal vehicle body. You can see the pattern is not perfectly omnidirectional like we would expect it be. As we travel down the road, you will notice signal fade ("flutter" or "waver") from this uneven radiation pattern. Co-phasing two antennas will even out the pattern irregularities. Instead of making the pattern more two directional, it will make it more omnidirectional. Do not expect more "gain" from two antennas. Figure 3 shows how co-phased antennas clean up the radiation pattern. Read the section "Co-Phasing" for instructions on how to make a harness to feed your co-phased antennas. It best to get them as far apart as possible. The best way would be to mount one on the front bumper in the center and one on the back bumper in the center also. Most people think this looks silly (me included!) and mount one on each side of the vehicle.

Enuff said?

 

The drivers who polled 4' single are correct. And why are you using a car?
To run dual antennas on a vehicle they need to be placed 102' a part. Which is not really possible with a 4 wheel if placed on the sides. And on a 18 it sends your signal more front to back. As I have stated in above post. Which you did not include. But you did include a car with co-phased antennas. And not the car with the single on the left rear bumper. In which the car with the Duals is compared too! The best place for a antenna on a car is the center of the roof, and not a bumper. I started in CB in 1968. And driving a Big truck in 1969. I admit that I don't know everything. But I do know something about 2-way radios and antennas. I don't need to take my CB to a so called repair tech to Peak, repair, adjust, or add channels in any radio. I can do my own work (and yes you can add extra channels to many CB sets made over the years. Not just Export radios). I install and adjust my own antennas and set SWR.
Now if you want to make a proper and fair comment you need to include why did the writer say what he did? And what it was compared to! If you really check the radiation pattern of co-phased antennas you will find that it's a fiqure 8. And not a full omni as shown in your picture. You need to include all facts and not just one little part of the puzzle. Just like you didn't include coax. Which is a very important part of the antenna system. Many, many truckers will use what they find in the truck stop for a dual antenna set-up. A co-phased RG-8X coax. Why? Because some so-called CB repair tech sold it. For duals you need 75 ohms and not 50. But most poeple are unaware of this. Now if you choose to run Duals you can. But I just feel that your comments and teaching about them is not 100%. And I DO know that the radiation pattern shown is not correct. It's a fiqure 8 and not a circle for that set-up. Go read and search for more info. And that link that you posted. Well if you want to buy what was said fine. But you really know about antennas before posting. Like I said, I don't know everything. But on this and many other radio topics I'm sure that I know more than you! And maybe the person who you quote. What I know about 2-way radios took years to learn. Now you need to go to a Electronics school and learn it before you can try teach it.
Also I find that most Ham would already know this and would not said something so dumb. I think your drum has a Hole in it!

 

After spending a few years trying different setups on the truck I drive, I have found that a properly setup and tuned cophased system works better then a properly setup single system.

 

Sorry BigM, didn't mean to upset you I guess you were not one of the truckers here sincerely trying to understand why their trucks come from the factory with dual antennas, but I will do my best to respond in order to clear up the nonsense you have propogated here with your hateful reply. Here goes:
"The drivers who polled 4' single are correct." -Nice opening, but you are dead wrong sir. READ THE LINK "we noted that the radiation pattern of a single antenna is "pulled" where there is the most metal vehicle body"

"And why are you using a car?"- I am not, but that rectangle there in the drawing does have "car" written on it, I admit, perhaps you need to blot it out and write "truck" there instead? Whatever helps in your understanding here, I am sure that scott 2RP789, the author and artist here, would not object:}

"To run dual antennas on a vehicle they need to be placed 102' a part. Which is not really possible with a 4 wheel if placed on the sides. And on a 18 it sends your signal more front to back. As I have stated in above post. Which you did not include. But you did include a car with co-phased antennas. And not the car with the single on the left rear bumper. In which the car with the Duals is compared too!" - actually, I quote above the following-"at CB frequencies the closest you would be able to place these antennas are about 18 feet apart" I stand by this dimension, NOT 102" as you state here. 102" is 1/4 wave, and having 2 antennas placed at only this distance apart would have no appreciable effect on RF radiation pattern from 2 placed 96" apart. I think you may be confusing the perfect mobile antenna, a 102" whip, with cophasing 2 short wound antennas for omnidirectional RF patterns. Please read the ARRL antenna book. BTW, in this poll, a 102" whip antenna is not an option, and for very good reason! You purport to be a truck driver in this forum, where do you have yours mounted sir?:} If you placed 2 102" whips 18 ft front to back on your truck for a true cophase setup, you could get your precious figure 8 pattern alright, but it would radiate its hi fields to your left and to your right, or BROADSIDE, of the antenna array, forward and back would be near null! I don't think as a trucker I am too interested in doing that, but you might be, to each his own:} Oh, yes, I am glad you noted the 102" whip that was mounted on the rear bumper in the diagram at the link I posted, but I have to ask, how far do you think your gonna get with it mounted on the center of the roof? :} I have a bro in law that acually tried that position once back in 1976, it was awesome in the driveway and out in the hayfield, but he was stopped before he ran into a power line overhead of road in town that afternoon by a local sherriff's deputy that pointed out the fact that he was about to kill himself with it:} The comparison illustrations on the link were between a 102" whip antenna and 2 shorter, more pratical antennas cophased, not a short antenna compared to 2 shorts cophased. Go back and study Grasshopper!:} All the shorter antennas that are practical to actually use on a truck (or car) are wound to acheive 1/4 wave, or the 102" dimension you seem to misunderstand in your reply to me here. "When a coil is added to an antenna it does three things. One, it cuts down on the antenna's efficiency. Second, it cuts down on the bandwidth. Third it cuts down the antennas impedance (it lowers it even more than 40 Ohms). The shorter the antenna is made, the more these three factors are reduced." (quoted here from the same link posted originally) So, I hope you understand that a single 4' antenna is actually a wound coil antenna to acheive 1/4, 5/8 wave, etc., and that you have some real efficiency issues when you actually use them that change RF patterns from theoretical. Let's move along here...

"I admit that I don't know everything. But I do know something about 2-way radios and antennas" - I am sure that this statement is true sir and I can't find anyplace in the post above or on the website I linked where there is a statement to the contrary of this, I apologize if I have missed this reference:}

"I don't need to take my CB to a so called repair tech to Peak, repair, adjust, or add channels in any radio. I can do my own work (and yes you can add extra channels to many CB sets made over the years. Not just Export radios). I install and adjust my own antennas and set SWR." - Ok, I'll take your word for that, but I fail to see any relevance to this poll in this statement. I thought Gadfly was out of line when he semmingly made fun of folks who wanted eport radios for "Extree Channels", I have never met a truck driver that had made any claim to have or to need this, but now I understand where all THAT got started, thanks:} ( apology to Gadfly is in order here} I have no need to participate in a pissing contest with you, but suffice it to say that I have an education and over 20 yrs under my belt as an electrician and engineer professionally. I now also have 9 yrs doing what I love, driving a truck OTR, under my belt as well. Oh, and no, I'm not a spring chicken anymore, but the grey matter still (in my opinion) exceeds my grey hair. I am sorry if you disagree, but I'm ok with that:}

"Now if you want to make a proper and fair comment you need to include why did the writer say what he did? And what it was compared to! " - This is something I can't understand...I linked to the ENTIRE WEBSITE in my post...you obviously actually WENT to the site, saw what you WANTED to see, and then proceeded to come back here and attack me personally as if I had insulted you by directing you there as support for the correct answer to the poll. Let's continue...

"If you really check the radiation pattern of co-phased antennas you will find that it's a fiqure 8. And not a full omni as shown in your picture. You need to include all facts and not just one little part of the puzzle. " - OK, see, this is where you are going wrong sir! You are correct of course in a Base Station array, this was also included at the site, neither the author or myself in any way disagree with you or anyone else on this, I also think this statement proves beyond a shadow that I met your criteria for "...why did the writer say what he did? And what it was compared to!" I am sorry if you misunderstood what the writer was talking about, and I don't really understand how you could confuse Base station with grounding and optimum sized antenna arrays with the clearly marked "mobile" tab on the site, but hey, go back and try is all I can recommend here. This poll has absolutely NOTHING to do with Base application of antenna theory, it is about MOBILE antenna application sir. By mobile we mean NO EARTH GROUNDING, and ANTENNA ARRAY SIZE LIMITED TO OUR VEHICLES, aka TRUCKS, and we are not given the choice to pick the 102" Whip!!

"You need to include all facts and not just one little part of the puzzle. Just like you didn't include coax. Which is a very important part of the antenna system. Many, many truckers will use what they find in the truck stop for a dual antenna set-up. A co-phased RG-8X coax. Why? Because some so-called CB repair tech sold it." - This poll is about antenna selection on a truck, it assumes all other components are the same. You really confuse me here anyway, I can't figure out what you are saying in this statement at all...are you mad at truck stops for selling 50 ohm coax or are you mad at some unnamed cb shop or "tech" for recommending it? BTW, at the risk of setting you off again, I will again direct you back to the site I originally linked here and recommend going to the home page there and clicking on the "Coax Basics" button on the menu to your left. All you need to know is there, including how to PROPERLY use 75 Ohm coax for the HARNESS portion of your antenna array when cophasing. See why I felt the need to post this in the first place? Again, you are half-right...the confusion by others with a desire to understand this question that you create when you make statements like the next one here in your attack:

"For duals you need 75 ohms and not 50. But most poeple are unaware of this." - No, sir, you are WRONG, you need 75 Ohm in the HARNESS section of the coax, you need 50 Ohm for the rest of it. Please read the material, all of it, not just what you want to see or THINK you know.

"Now if you choose to run Duals you can. " - Why thank you very much sir, I definitely will! :} I will also try to understand WHY I do that, and I will try my best to help anyone interested in this subject to find their own answer without adding to their confusion with half-truths and irrelevancies.

"But I just feel that your comments and teaching about them is not 100%. And I DO know that the radiation pattern shown is not correct. It's a fiqure 8 and not a circle for that set-up. Go read and search for more info. And that link that you posted. Well if you want to buy what was said fine. But you really know about antennas before posting. Like I said, I don't know everything. But on this and many other radio topics I'm sure that I know more than you! And maybe the person who you quote. What I know about 2-way radios took years to learn. Now you need to go to a Electronics school and learn it before you can try teach it.
Also I find that most Ham would already know this and would not said something so dumb. I think your drum has a Hole in it! " - You have the right to believe the world is flat, I don't care, nor will I attack you for this belief, even though I don't believe like you do in that matter. I posted my answer and the supporting documentation for this poll sir, I am sorry if you took offense to a scientific approach to this poll, and I am perfectly willing to study anything you recommend IF IT APPLIES TO THIS POLL about selection of MOBILE antenna for truck use. As for personally insulting you, I have to pass on that, no topic is worth that to me...apparently we will have to disagree on that point also:{

 

Interesting .....

I ran dual wips on 52.525 with a phasing harnest to give me a multidirectional array .

How did it work ?

Not worth all that money ..... I just don't buy into dual antennas if i did my car would again have them .....

 

I agree with you WA4GCH, on HAM bands you can get more for your money certainly by spending it on watts output usually. The dual antenna thing for mobile CB application on trucks is used primarily to get a more omnidirectional RF field due to the sheer size of the vehicle (pull on the field). This is really the only advantage that duals have in this application, but it is an advantage:} I got a kick out of the whole left/right single antenna placement thing on another thread, and I felt sorry for Jolsen who actually had very good points that were dismissed way to quickly in my opinion. It actually makes very little difference which side of the truck its mounted on, the vehicle is going to cause a pull in its RF field toward the truck on either side. A truck has a BIG effect on RF fields and this is the reason truck manufacturers have started equipping new trucks with the dual antenna setups. Truck manufacturers dont design ANYTHING into a truck without a GOOD reason, and they pay a lot of bucks to a lot of engineers to study what is the best for the truck application.
I am sure you realize why the dual 102's in the mobile application you mentioned above didn't work out so well, I know you have studied antenna theory just by your handle on here! Heck, I bet you even have a copy of the ARRL antenna book!LOL
I guess I am just a guy that's crazy about understanding why I do things, and I am goofy about details, wish I could turn that off sometimes, (like before I tried to help here), and I am open to learn more ANYTIME.
I am very impressed that you attached that pdf file to your post explaining your position, I thought it was such a good idea I tried the same thing also to help explain my position! I wish anyone that posted a vote HAD to do that, that way, we might ALL actually learn something. I know I have learned a lot already about things I THOUGHT I knew since I decided to participate in this poll! I just need to learn how to share my newfound eureka moments in a way that doesn't irritate folks. I really apologize to ALL here if I have upset them with what I have learned, I am sincere.
I just hope Jolsen reads all this and realizes he knows a lot more than some folks seem to think he does and does not lose his apparent interest in pursuing HAM radio as a hobby. I use Jolsen as an example here, go back and read what has been posted to him and his frustration with the confusion that was created by responses he got on the left/right single antenna discussion. I was appalled...there are too few new radio ops coming into the ranks these days due to cellphones and internet, we sure don't want to discourage any prospects by appearing to be condescending and pompous just because we took a test 30 yrs ago and passed! Radio ops may be dinosaurs now, but what happens, heaven forbid, if all this newfangled cellphone/internet technology does not work in a time of emergency? It does happen.
Anyway, enuff on the soapbox for me, good to meet you all, and thanks ALL for helping me learn about mobile antenna theory:}