co-phase vs single antenna

[roadrage]

I have read over and over about co-phasing antennas on passenger trucks not being as good as good as a single antenna. I have a co-phase set up on my fishing truck. I liked the look of it and didn't need that truck to Xmitt more than a couple miles. I had the whole antenna system was given to me by my father-in-law, so I didn't have anything to lose by hooking it up. It acutally works pretty well. Both my Grant and my Cobra 29 seem to pull in DX signal better than my Wilson 1000/Galaxy 95t2 on my other truck. So I decided last night to do a basic test on the difference in performance on my truck between co-phased and single.

The set up as it sits is:
1996 Ford F150
Cobra 29 WX ST NW
Archer 4' flex antenna
Rg59 co-phase coax

My testing:
I will drive out to set distance from my second truck 2 mi, 4 mi, and 6 mi. At each distance I will perform a radio check with my son. Each of us will transmitt while the other records S meter readings. I'll turn the truck 90 degrees and repeat. Then the RG59 will get disconnected and replaced with RG58 to a single antenna. Then perform another radio check and record both S meter readings. I'll turn the truck back 90 degrees and re-check. Then I'll drive to the next distance and repeat.

I'll post what I find on how much difference it makes in each spot between 1 antenna and co-phased, for my application.

 

[The DB]

Where a lot of people put cophased antennas on pickups is about the worst possible place. Generally the cab is directly in front of the antennas themselves.

At 9' the gain for cophased antennas is about 1db. That is about 25%. That is also assuming lab conditions. As the antennas get closer and closer the gain drops and the radiation pattern acts more and more like one antenna.

There are other things at play that are rarely discussed that also affect the antennas, such as mounting position as I mentioned above. Where an antenna is mounted on a vehicle can drastically affect the radiation pattern as well as efficiency. There is also a decreased in efficiency simply because you are using two antennas instead of one.

Based on my experience I don't think you will notice much difference going from the cophased antennas to a single antenna mounted in the place of one of the previous two. I bet you would notice more of a difference going from a typical cophased setup on a pickup to a single antenna mounted on the roof.

I also recommend checking the tuning on the single antenna when you switch to it. Remember these antennas were tuned to work together. There is no guarantee that the antenna will be tuned as well when running by itself.


The DB

 

[roadrage]

I'll definately be bringing my meter with me. I do intend on keeping the antennas right up on the mounts they are on. The roof is usually the best place for an antenna. For that truck it isn't but not for performance reasons. I don't expect much to last long on the roof when I am crashing through trees and blowdowns. I am pretty rough on the old girl. If I did have a single antenna, it would be sitting right where one of the two are now.
I do have them set about a 8" above the bedrail, on a home-made mount. I wanted the antenna to be as high as I could get them without worry of their destruction. I have almost 3/4 of the antennas above the roof (the Ford). As it sits, I can (and do) scrape the roof with a low limb and still not break the antenna.



I do have to delay my little experement til tomorrow though. No baby sitter for my toddler, and the wife is working til 9:00.

 

[trailrider]

maybe it's a texas thing or a trucker thing or just my thing' but even if they don't work as well. I just gotta do the duel set-up on my pick-ups.

 

[roadrage]

maybe it's a texas thing or a trucker thing or just my thing' but even if they don't work as well. I just gotta do the duel set-up on my pick-ups.

Honestly, I was talked out of the duals when I was getting my set up for this truck. But before I was able to buy an antenna, someone happened to have the entire co-phase set up lying around. From the whips to the coax, mirror mounts, etc. It was free so I wasn't going to turn it down. I had planned on changing it when I had the extra cash to spend, but it has been years and its still there. It honestly works pretty decent. I can't complain. How much better would one antenna work? I'll find out when I do my little experiment.

One thing I've seen people do is run one antenna and the second is just there for looks. They just use 50 ohm coax going to the one and leave the second antenna unconnected. Most fiberglass isn't too expensive.

 

[The DB]

I have nothing against cophased antennas, its just in my experience they are a lot of extra hassle for what little if any real gain you get out of them. If they work for you, by all means, use them.

That doesn't mean I'm not a fan of phasing. Yes, there is more to phasing than just cophasing. I prefer end fire arrays personally. A properly set up end fire array at 4.5' can net you over 4db (about 150%) gain to the front. Mind you that type of setup isn't always the best for small roofs like most semi's or pick up trucks. Generally I see them on SUV's, usually done with predators, but I've seen it done with 102's as well. They can be even more of a pain than cophasing with their different lengths of coax, but there is significantly more gain involved.


The DB

 

[roadrage]

I was quite lucky that the antennas were already tuned when I received them. I drilled some holes and bolted them on where I wanted them, and 1.3 on ch1 and 1.4 on ch 40. I ain't running power, just a barefoot Cobra 29, so I left well enough alone.
If I was to put an amp in that truck, the antennas would have to come down. I doubt they have a high power rating, and I'd want a better antenna match than what I have. I'd want it 1.1 or 1.2 so I' would go with a single whip in that case.

But I'm not trying to convince anyone one way or the other. I have always read that co-phased isn't as good as a single antenna. I decided that I want to see just how much a difference it makes, apples to apples. I wouldn't mind throwing an orange into the mix by removing one side and mountind it top/center of the roof and compare it to the current locale as well. But that is just too much effort with the amount of time I have. I will be happy with whatever my findings are. Either way it goes, I'll have learned something.

 

[mr_fx]

co phasing is a huge waste of time on a passenger vehicle it's just something the hill billies do to make their truck look awesome. But even worse I guess is when the truck drivers think they have to turn their antennas downward to make the 'bull's horns' At least big trucks 'might' benefit from co phasing, but in most cases it doesn't even matter esp after they make those 'bull's horns'

 

[The DB]

I was quite lucky that the antennas were already tuned when I received them. I drilled some holes and bolted them on where I wanted them, and 1.3 on ch1 and 1.4 on ch 40.

I bet with a little work you can get an even better SWR.

co phasing is a huge waste of time on a passenger vehicle...

I don't disagree with this part of the remark, however, the op wants to see for himself so more power to him.


The DB

 

[Watergate]

co phasing is a huge waste of time on a passenger vehicle it's just something the hill billies do to make their truck look awesome. But even worse I guess is when the truck drivers think they have to turn their antennas downward to make the 'bull's horns' At least big trucks 'might' benefit from co phasing, but in most cases it doesn't even matter esp after they make those 'bull's horns'

I can say I have gained one benefit from cophasing that I can see. I run up a twisting steep canyon road to get loaded, and without the cophased antennas my signal was getting blocked by a mountain side and my trailers. Not terrible, but enough to make calling ahead to see where other trucks were on the tight corners a pain. RF gain all the way up, and squelch all the way down, and listen to the static for the whole trip.

With the cophased antennas, I can squelch the radio. Just a matter of terrain blocking the signal.

I always laugh at the bull horn antennas on trucks. Purely for bad looks most of the time. Sometimes its a height issue, but if I am going to hit my antennas, my exhaust stacks are right behind them and will hit too.

Sent from my DROIDX using Tapatalk 2

 

[KM3F]

Co-phasing antennas.
At 11 meters, a 1/4 wave distance is about 8 feet.
The antennas need to be at least 8 feet apart to realize any gain benifit. Even then the radiation pattern is not circular but close to a figure 8 pattern when the distortion of the pattern is taken into account from the vehichle they are mounted on..
On the big trucks they may be able to get them 8 feet apart by the time you get to the outboard edges of each mirror, but not on a smaller vehichle.
Mostly besides looking cool there is little benifit on a car or small truck of having them much less than 8 feet.
What is never realized why this works this way is the power from each antenna has a distance vs 'phase' relationship that does various additions and subtractions that form the shape of the pattern.
.
Lastly the upward angle of the pattern is mostly determined by the height off the ground on the vehichle, the element length and by the vehichles body's capacitive coupling to the ground under it.
Bottom line it there are a lot of parameters at work in any installation.
Good luck.

 

[roadrage]

co phasing is a huge waste of time on a passenger vehicle it's just something the hill billies do to make their truck look awesome. But even worse I guess is when the truck drivers think they have to turn their antennas downward to make the 'bull's horns' At least big trucks 'might' benefit from co phasing, but in most cases it doesn't even matter esp after they make those 'bull's horns'

You are really calling me a hillbilly? It is funny all the name calling that happens on this site. I thought it was us "CBers" that are supposed to be the trashy trouble makers. The first name calling always seems to originate elsewhere. Weird?? People like you make this forum look bad. I am glad that you feel so superior.
As far as to co-phase or not, we'll see just how much of a negative impact it has. Have you ever tested as to which is better? I'll bet not. You just read it everywhere, like everyone else. I guess that if everything depended on logic and theory, science would have no use for experimentation. They could simply say "it doesn't make sense, so it can't be true." I suppose that if that really was always true, we'd all still think the Earth was the center of the universe; and there'd be no-one but Native Americans living here, because we'd all still think the Earth is flat. At the end of the day, it very well may be true. But how exactly does that justify you being so rude?

And furthermore, this is something that I thought might be fun for my son and I to do together. As a Christian, I forgive your remark. I hope you know that if I thought you were doing something that I didn't agree with, surely I wouldn't put you down.

 

[mr_fx]

offended brother. The bible tells you not to take offence <gotproof>

I have plenty of Hill Billy (and they are proud of it too) friends, even they agree co phasing on a passenger vehicle is just for looks. If it floats your boat then do it.

Don't take my opinion to heart brother, I mean I use baling wire for antennas, now that is hill billy

As for have I tested the difference, I really don't have to, the antennas are too close, it's simple math...

co-phased uses a 75 ohm coax, so even if you get a perfect match on the antennas(which you won't) you automatically start out with a 1.5:1 swr

that being said I have read many true reports, and I HAVE tried it myself, in my case the signal with 2 antennas co phased was lower on output by almost 1 full s unit according to 3 different local stations and 2 DX stations, but this was a long while back

I mean what are you hoping to achieve?

 

[mr_fx]

KF3M hit the nail on the head, I guess you could put on at the front of the vehicle and the other at the rear...

 

[mr_fx]

I don't disagree with this part of the remark, however, the op wants to see for himself so more power to him.

The DB

Mr DB I totally agree, that's the fun part is playing around, the sad part is when you got this antenna you can't sell so you just keep using it even if it does nothing for you (or in my case made it worse)

To the OP make sure you test the single antenna against the duals at or around the same time with the same people

and OP as for your comment about experimentation, that's not experimenting, it's all been done before, it's old news... however there is a term for someone that does an act and expects different results even though the variables have not changed...

good luck OP