Anyone ever run circular polarization? what did you think?

[loosecannon]

I have a friend who is putting up a tower and considering this option.

We were talking about installation since i will be helping him, and he asked me about it.

I read the paper that Lou Franklin put out decades ago, and i understand the concept, but i have no real-world experience in running an antenna that is fed this way.

so, what are/were your experiences with circular polarization?
LC

 

[Captain Kilowatt]

I assume you mean for CB? I would not do it. TRUE circular polarity is much more than simply connecting the V and H feedlines together. You must have a delay line in one feedline and which feedline has this delay line determines whether you have left hand or right hand circular polarity. You really need to be able to switch between the two. The gain of a single yagi in conventional orientation looses 3dB when set up as circular however it will respond to rotational fading very well. I can't really see any reason for doing this on any HF band but it is very commonly used on the VHF and UHF amateur bands especially for space comms.

 

[The DB]

The question I have is why are you looking at circular polarization? Aside from satellite work its use is very rare, and if you want to use is for regular DX/local contacts it won't work quite like you think it will.


The DB

 

[Captain Kilowatt]

The question I have is why are you looking at circular polarization? Aside from satellite work its use is very rare, and if you want to use is for regular DX/local contacts it won't work quite like you think it will.


The DB

Also IIRC if you TX LHC the RX station must use RHC so in this case different polarity must be used on opposite ends. I may have that wrong as it has been YEARS since I last dealt with circular polarity and then it was only minor. I may be thinking that occurs after the signal is reflected off something but that would include the ionosphere so for HF DX purposes it would be senseless.

 

[Robb]

I agree with CK.
To CB, gain is everything - IMO. I would rather use an antenna with substantial gain ('beam') - rather than needlessly create interference with my home and others homes around me - by using an amp to make up for gain. Better to run two feed lines and an antenna switch to have both polarities available than to compromise a few db's just to have circular polarity.

In addition, one would need to agree on a convention of left to right or right to left to make it practical to those that want to use it. Which means that one would still be better off having two pole beam with an antenna switch.

 

[543_Dallas]

With a beam you can pick which neighbor to bleed on.

 

[Robb]

Never had a single neighbor complain.
I run a clean radio and it works out fine.

On the other end during skip conditions, operators assume I am using an amp. You can almost hear them scratch their heads and get a puzzled look on their face when I tell them it is a stock radio with a horizontal 4 element Yagi. They say: yeah, sure . . .

 

[nomadradio]

Lou Franklin's setup is the same one hams use for satellite operation with crossed yagis. The signal is split between vertical and horizontal, but with a longer coax to one of them than to the other. The signal is delayed through the longer coax and has the effect of combining vertical and horizontal polarization. Not strictly the same circular polarization you would get from a helical antenna, but close.

The reason for doing it with a satellite antenna is the Faraday Rotation. This is the tendency of the upper atmosphere to rotate your polarization as it passes through. This is what causes most of the fading of skip signals. An antenna that responds equally to vertical and horizontal signals will reduce the fading of a distant signal. A satellite signal will do the same thing, with the polarization "rotating" continuously around its axis.

73

 

[loosecannon]

Honestly the only thing i have ever read about CP is the paper Lou put out, and that was almost 30 years ago, so i really don't remember the details.

To me, the entire attraction was that you could reduce or eliminate skip signal fading due to the polarity rotating.
My question is/was to what degree this helped.

I had completely forgotten about the DB loss involved, if i ever knew about it, but it does make sense.

For those reading this thread that may not be familiar with Lou's write-up, it wasn't an antenna design with circular elements resembling a slinky.
It was a way of feeding a dual polarity beam so that the signal came out rotating (from what i remember).

the only reason i was even thinking about it was that a friend had asked about this option for his new beam, and i didn't know enough to really advise him.

sounds like the consensus is that it just aint worth it.

Im still hopeful someone will join the thread that has actually tried this on CB.

also, if anyone has a copy of that old write up, I would like to read it again.
LC

 

[Mustang 131]

circular polarity = 3db less gain in the real world.