http://www.astronwireless.com/topic-archives-antennas-polarization.asp Maybe this will help clear up some of the confusion I am reading here. It may make it even worse? LOL
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Horizontal and Vertical -Same Time.
- Thread starter silvereagle1
- Start date
CP benefits satellite communications much the same way it benefits HF skywave propagation. Because the satellite signal passes through the ionosphere its polarization is distorted and twisted as is passes through just like a skywave signal when it reflects off the ionosphere.
What determines the difference in LCP or RCP is what side of the antenna has the extra 1/4 wavelength of coax in it to delay the signal. The direction of CP is only important when you are dealing with another signal that is also CP like with satellites. On 11 meters there are just about no CP stations so either direction of rotation will show the same results there.
The SWR is always a problem when combining two 50 ohm antennas directly together through a switch box since the end result is a 25 ohm load and a 2:1 SWR. That is easily corrected by feeding both sides of the antenna through a 75 ohm co-phase harness.
What determines the difference in LCP or RCP is what side of the antenna has the extra 1/4 wavelength of coax in it to delay the signal. The direction of CP is only important when you are dealing with another signal that is also CP like with satellites. On 11 meters there are just about no CP stations so either direction of rotation will show the same results there.
The SWR is always a problem when combining two 50 ohm antennas directly together through a switch box since the end result is a 25 ohm load and a 2:1 SWR. That is easily corrected by feeding both sides of the antenna through a 75 ohm co-phase harness.
Ok, enough circular reasoning
What he asked was simultaneous vertical and horizontal.
Circular polarization requires a 90 degree phase shift which technically isn't simultaneous.
What I've found works best is vertical for local base to mobile and base to base comms, but horizontal for DX TRANSMITTING and DUAL (simultaneous) polarization for DX RECEIVING only.
I've found horizontal polarization works best for DX transmitting because the best gain seems to be had by the 6+dB ground gain afforded by horizontal over vertical, but also, horizontal seems to approach the F layer more effectively than does vertical, however, I use the mix position on my switchbox when receiving to avoid the deep fading of DX signals as they pass through one polarization to another, and back, as Shockwave pointed out in a previous post.
Perhaps another thread could be opened to discuss the finer details of circular polarization, it is an interesting option,
- but simple dual polarization is a different option and actually requires IDENTICAL coax type & lengths to achieve, otherwise it's headed in the direction of circular polarization.
I hope this helps simplify not confuse.
What he asked was simultaneous vertical and horizontal.
Circular polarization requires a 90 degree phase shift which technically isn't simultaneous.
What I've found works best is vertical for local base to mobile and base to base comms, but horizontal for DX TRANSMITTING and DUAL (simultaneous) polarization for DX RECEIVING only.
I've found horizontal polarization works best for DX transmitting because the best gain seems to be had by the 6+dB ground gain afforded by horizontal over vertical, but also, horizontal seems to approach the F layer more effectively than does vertical, however, I use the mix position on my switchbox when receiving to avoid the deep fading of DX signals as they pass through one polarization to another, and back, as Shockwave pointed out in a previous post.
Perhaps another thread could be opened to discuss the finer details of circular polarization, it is an interesting option,
- but simple dual polarization is a different option and actually requires IDENTICAL coax type & lengths to achieve, otherwise it's headed in the direction of circular polarization.
I hope this helps simplify not confuse.
I dunno about that,you seem to be mixing horizontal beam antennas Vs vertical antennas and horizontal polarization Vs vertical polarization.
That 6 Db ground gain doesn't apply to F layer paths, (or even Es paths).
As far as the F layer (both F1 and F2), the vertical antenna has a lower TOA and will have a better DX skip distance than a horizontal beam when both are at the same height.
A horizontal beam may produce a better SNR than a vertical antenna because it is not affected (as much) by man made noise which is mostly vertically
polarized.
It would seem to me that dual polarization would divide the current between the antennas because they are in phase. Circular polarization would allow each antenna to get full power because they are taking turns. Would this assumption be correct?
The dual polarization splits the current between the two radiators. This causes each one to be 3db lower for each than if the same power was going to a single radiator. But by having two radiators, there is more radiator in the air than a single. Two radiators each given same power as one will be 3db stronger. So in effect, splitting power between two radiators would be the same total radiated power as the same power applied to a single radiator. What are everyone's thoughts on this?
The dual polarization splits the current between the two radiators. This causes each one to be 3db lower for each than if the same power was going to a single radiator. But by having two radiators, there is more radiator in the air than a single. Two radiators each given same power as one will be 3db stronger. So in effect, splitting power between two radiators would be the same total radiated power as the same power applied to a single radiator. What are everyone's thoughts on this?
No. The power is still divided in circular polarization, its just the half of the power is delayed before it gets to the antenna. You will still be down 3dB to vertical and horizontal polarization...
The DB
Except on CB. CB operates outside all the rules. We know that...
As in 11m, you can co-phase verticals on your vehicle? We have co-phased the same antennas horz. and worked. If you place the antennas at 45 deg angle it will allow operation both vert. and horz. Have never done the later, but have a friend who swears by it. So if you co-phase one vert. and one horz. ? I just do know, seems like a cancelation, as though they would both rob Tx and Rx.
If you place an antenna on a 45 degree angle it's responsive to both vertical and horizontal but you'll also be about 3db lower than if the polarization matched perfectly. If you're off by more than 45 degrees the signal drop increases rapidly up to 20db loss at the complete cross polarization point. You'll still get the same 20db drop in skip when the polarization of the signal is at the exact opposite 45 degree angle.
Using the 75 ohm co-phasing cable and combining them both together is just vertical and horizontal together. Adding the 1/4 wave, 90 degree phase delay line converts dual polarity into full circular polarization. That makes your signal resistant to all polarization shifts in DX. There is no cancellation of the signal as the two combine together in the far field as CP.
Using the 75 ohm co-phasing cable and combining them both together is just vertical and horizontal together. Adding the 1/4 wave, 90 degree phase delay line converts dual polarity into full circular polarization. That makes your signal resistant to all polarization shifts in DX. There is no cancellation of the signal as the two combine together in the far field as CP.
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Thank you. I'm not that smart. Would that make it better for RX and Tx?
Have a vert. omni up now and building a CQ and switch box to swap between the two. Wondering if I should addend my build of Quad to include switching for vert. and horz. and bi-polar.
Here is another question: the circular polarization harness is normally put at the antenna but what if it was put in the shack? If the antenna already had two coaxes going to the shack, it would be easier to play with the harness in the shack. Once the phase is shifted, it should stay that way if both coaxes going to the antenna are the same?
Good point. You want to have the phasing take place in the shack. That's the easiest way to obtain the most options. Choosing flat, vertical, both together, RCP and LCP just by changing coax and which one gets the 90 degree delay. Plus, all of those connections are out of the weather and easy to get at if one fails.
Wel,.if it is your friend that talks about them be co-phased, consider the source
Wel,.if it is your friend that talks about them be co-phased, consider the source
I have.
Ole' BS maker when whiskied. He recently converted to a 102 whip because it just wasn't cutting it. Guess he saw that mine was better.
One of these coax switch boards would be perfect.
https://www.mfjenterprises.com/Product.php?productid=MFJ-4706
I wonder if it would hurt anything to coil up the harness to neatly plug into this?