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Discussion in 'CB Antennas' started by silvereagle1, May 23, 2012.
Hi All. Dose anyone run the beam's Horz an Vert at the same time and if so why? Or why not. Thanks.
Maco Circular Polarization Harness
For users who want to achieve circular polarization on their dual polarity beams. The
hand-soldered Maco Circular Polarization Harness allows you to run your vertical and
horizontal gammas at the same time. Perfect for all Maco Dual Polarity Beams, Gizmotchy
Beams, Moonrakers, PDLII,
New Products from Maco Antennas
Hey Robb, can you describe this harness a bit more?
Well, besides its general description - this harness combines the use of both gammas on the vertical and horizontal beam elements. Never used one; my beam is a Yagi with only one gamma - of course. But what this harness is supposed to accomplish is causing both the vertical and horizontal elements to radiate at the same time. Bet it is a bear to set up! But the net result is a circular radiating pattern if phased correctly.
Perhaps you can put this one into EZNEC and see how that radiates.
Perhaps using a PDL-II as the basis for that model?
I suspect that this is just the old familiar co-phase harness that Maco sells to stack a pair of yagis or V-quads, but with a new name. Since Maco markets their "Dual-polarity" yagis (a horizontal and a vertical beam on the same boom), it follows that a co-phase harness could be used to drive both antennas simultaneously in order to get circular polarization.
So you don't know anything about it, so I try this. Why would anybody want to use CP with its very limiting useful purposes?
I've always thought the vertical and horizontal elements had to be fed slightly out of phase to achieve circular polarization????
You are correct:
This is from Signal engineering`s web page, the whole thing is here:
The Ultimate Guide to 11 Meter CB Antennas
Also Note this part, that I think Marconi is talking about.
The Harness that Robb linked to has the following description:
Most of the time, you will find Amateur Satellite operators using these type of antennas, I do not see much of a advantage of using them on CB unless the guy you are talking to is also using the same thing.
I intend to do a couple of crossed dipoles like this in the future. I have bookmarked some info somewhere about it.
It is supposed to result in a 3db loss of TX, but that is less than the loss caused by fading at times, so I want to try it . . .
I can always do what I do and take it apart for something else.
wouldn't it need 75 ohm coax from the switch all the way to the antenna feed-points ?
Yep. From the T where the harness splits to the antenna. There isn't a switch because they both transmit and receive at once. From the harness back to the radio is 50 Ohms coax.
Nope; don't know much about how it hooked up with the beam other than plugging it in. Like I said, It is probably a bear to go back n'forth between the gammas unless the harness comes with some paper to describe what you are trying to do. Interesting to try it though. Lou Franklin sells plans for a kit to build a circular polarized antenna. Looked interesting . . .
From Lou's site:
". . . Improved performance on skip signals.
Improved performance in hilly areas, or between tall buildings.
Talk to mobiles (vertical) or bases (horizontal or vertical) automatically and without switching.
3-element beam design gives 7 dB gain over a dipole.
Simple construction with common materials. Detailed, non-technical assembly and tuning instructions.
Circular Polarization (CP) is an idea borrowed from FM and TV broadcasters, who were faced with the problem of getting out to both cars (vertical) and homes (horizontal). CP is basically a rotating, twisting radio wave containing properties of all polarization angles, including all those in between vertical and horizontal. (Such as skip signals, signals from moving mobile whips, or signals bounced off hills or buildings.) Regardless of the antenna type used, most CB signals change their polarization as soon as they bounce off an object. With CP, it doesn’t matter. You’ll get out better and hear better, even if the other station is using a conventional antenna.
The other big advantage of CP is its elimination of multipath fading. You’ve probably experienced this as "ghosts" on your TV set when an airplane passed overhead. Or as fading when talking to a moving mobile. Since CP receives all polarization angles, it doesn’t matter what happens to the other station’s signal on its way to you. And when transmitting, the fact that your signal contains all types of polarization increases your chance of being heard by both local and skip stations. Finally, add to this the 7 dB beam effect. This is equivalent to a five-fold power increase! (A 4-watt CB sounds like 20 watts!). . ."
Thanks to all keep it comeing I am takeing note's
The Ultimate Guide to 11 Meter CB Antennas states correctly about the 90 degree phasing harness, however the choice of cable will make or break the operation. RG-133/U (95 ohm) is the best to use for the harness. RG-63/U (125 ohm) is easier to find but causes more of a mismatch when used with a 50 ohm main transmission line. RG-59/U cable is used for co-phasing antennas to obtain gain, not for a circular polarized antenna system.
As was stated in one of the responses: When using circular polarization the signals are down 3 dB in each plane as a result of the phasing harness. Thus to get the same range results for a 100 Watt system using either Vertical or Horizontal polarization, will now require a 200 Watt transmitter.
It's all academic since it has been shown that a skywave signal starting as vertical or horizontal will arrive as an elliptically polarized signal anyway. That was discussed several months ago in a QST article.