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Co-phasing an Omni-Directional Antenna with a Directional antenna

DualAntennas said:
Not Trolling I come from a family of truck drivers we're all about the Dual's.... Breaker...Breaker.... 1-9 for a radio check......

Trucker Language............

Break = I wanna talk

Go Break = Come'On Boy Talk!!!!

Most of us C B'er's are Country Boy's making Southern Conversation NOT HAM's
Click to expand...


Most truckers know that dual antennas are mostly for looks,you know symmetry. They rarely ever work better than a single decent antenna on a decent mount.A lot of those dual antenna set ups really only have one antenna connected. Besides what does dual antennas on a truck have to do with good omnidirectional coverage on a base which is what you want? As for asking others to do your testing for you.....why? Do it yourself and learn in the process.
 
I modeled this idea as I understand it. I co-phased (phased) using a 12' foot 75 ohm phasing harness, with an attached 50 ohm feed line that was set to actual length to the ground.

I see these models present a little ill-effect to the Yagi's pattern, but it's not nearly as bad as most here suggest. I don't think this setup benefits the idea of gain as noted by the reference to a keyhole antenna either...whatever that is.

The higher gains noted with the 1/2 wave and the 5/8 wave ground plane models are probably elevated by their higher SWR due to unmatched models. The 1/4 wave model shows a very good match, and thus this is what models tend to do with a better AG result. The gain for such models are typically lower and more accurate, so if these models with longer radiators were matched...the differences in gain might be closer to the 1/4 wave model.

These models were not built to any specifications except the lengths were close to the math used, and I did not try and tune the phasing harness. I just used a length I found worked with 102" inch 1/4 wave whips. The Yagi I used was a random model that showed a pretty good match, and I just added the vertical ground plane antennas to the reflector element...like I would do with a dual polarity Yagi beam model. I did not bother with modeling these in Free Space, but the individual models standing alone all show an acceptable AG results.

http://img10.imageshack.us/img10/8573/q6r.pdf
 
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Eddie, a keyhole pattern from an antenna is shaped just like a keyhole in tbe old locks. Sort of round at one end and elongated at the other. I see your plots above but I don't see a horizontal azimuth pattern. Just elevation plots. Also you have the model wrong. The model should have the omni completely separate from the yagi and not positioned by the reflector element.Both antenna are to be of the same polarity also. Antennas like this are only used where omnidirectional patterns are wanted but coverage in one direction is poor or to extensive coverage into a neighboring town beyond the range of the omni antenna. They are mostly used on repeaters and even then very rarely as good high gain collinear verticals are available.
 
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DualAntennas said:
Most of us C B'er's are Country Boy's making Southern Conversation NOT HAM's
Click to expand...

CB language... excuses excuses... I bet 95% of people who post in this CB forum we are posing in speak it well.

You would be surprised at how many cb'ers come from cities. You may also be surprised at how many hams started out as cb'ers, including myself. You may still be surprised at how many of us hams still have and use a CB.

I am fluent in the CB language, although some things used in the CB language seems designed to have the same effect as "leet" speak. Examples used in another thread are "bounceback system" and "two hotts", I"ll throw in "pill" here as well as another example. The term "cophased" translates into english as two identical antennas side by side fed in phase with each other with a pair of 75 ohm coax lengths. That is what it meant 20 years ago and that is still what it translates to today. Further, most people who use term have no idea why that setup works, they simply know it does. All of your threads use the term heavily yet only one of them actually use it in the context of "cb speak". Further, I think a lot of the reasons some people use "CB speak" for some things is they often don't know any better, or think it is the actual correct terminology.

As I said above, if you really want to know what is going on with antennas you will do the work. We may be able to give you an idea, but you will never truly be able to understand the ideas mentioned without at least some understanding yourself.

Also, keep this in mind. As I have said multiple times above, when you run two antennas from the same source they each take half of the available power from that source. If they are not in some very limited arrangement of setups you will have nothing but losses.

Captain Kilowatt said:
Most truckers know that dual antennas are mostly for looks,you know symmetry. They rarely ever work better than a single decent antenna on a decent mount.A lot of those dual antenna set ups really only have one antenna connected.
Click to expand...

I used to do antenna work for a CB shop back in the day for extra income. I have worked and learned on trucker antenna setups and can tell you for certain that the bold text in the quote above is absolutely true. Less than 25% of truckers that passed through here with two antennas on their trucks actually used both from a single radio.


The DB
 
The DB said:
Claiming you don't have the time doesn't impress me or anyone else. I can think of any number of other things to do with my time other than study antennas, make models, build antennas, and check these forums. If you really want to know about antennas and how they work YOU must take or make the time to learn about them. There is no substitute for time spent researching and studying, and I cannot do that for you.

The DB
Click to expand...

Legend and Wikipedia tell us that the great Greek mathematician Euclid was trying to explain geometry to Ptolemy I, ruler of Egypt after the pharaohs. Ptolemy was getting frustrated at the amount of concentration he needed for this (at that time) new branch of math and ordered Euclid to explain it better because he - Ptolemy - was the King! Euclid's reply:

"There is no royal road to geometry".

Nor is there any royal road, or "Antennas for Dummies" road, to antenna physics. Experiment! If Marconi had had forums like this back in his day, he might well still be wondering if his wireless antenna would "work".
 
DualAntennas said:
Not Trolling I come from a family of truck drivers we're all about the Dual's.... Breaker...Breaker.... 1-9 for a radio check......

Trucker Language............

Break = I wanna talk

Go Break = Come'On Boy Talk!!!!

Most of us C B'er's are Country Boy's making Southern Conversation NOT HAM's
Click to expand...


You come from a family of truck drivers who are all about duals?
I don't believe anyone is buying this, but nice try.
 
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