The difference between a Linear and Circular LNB

[skytec]

What is the difference between a Linear and Circular LNB?

This has to do with the way the signal is transmitted from the satellite in the sky. There are two different ways that a satellite can broadcast its signal. If linear, it broadcasts Horizontal and Vertical. If circular, it broadcasts Right Circular and Left Circular. To understand this better, imagine the signal coming in like a screw that's turning left or right.

[satman72]

Re: The difference between a Linear and Circular LNB

Circular polarity is now going to die, it is used just by some old satellites all new satellites uses linear polarity. It was used much in past expecially by satellites was covering north Europe like Thor and Tele X.

[nev]

Re: The difference between a Linear and Circular LNB

My understanding is that either dish type can receive either type of signal. What makes the difference is the LNB. That has to be specific to the type of signal.

[dmgp]

Re: The difference between a Linear and Circular LNB

I don't think circular polarity is going to die, as I believe the new Ka band transmissions for the republic of Ireland will utilise this system. Way back when we had adjustable magnetic polarisers it was possible to receive right and left circular polarisation on 'normal' vertical/horizontal LNB's although with some signal loss.

[besit]

Re: The difference between a Linear and Circular LNB

I always thought that circular polarization is used only by Russian money-loving-so-much pay tv providers - НТВ+ and Триколор, both on 36E, all Left for Tricolor and All Right and some Left for NTV+. It seemed to me that they use round polarization to prevent their customers from watching other channels in line polarization from same satellite. I got a little dish 60cm with round LNB looking on 36E, but I don't watch it for these packages work not so good with satlover 3rd server.
There were some posts on Russian SAT forums, how to make modifications to LNB to make it possible to work in round and in line polarizations.

[besit]

Re: The difference between a Linear and Circular LNB

OK, there's not much materials in English over internet about round/linear polarization because i think a lack of need in round polarization in the West.
- I found some information about some Invacom LNB
Specification's here _http://www.galaxy-marketing.com/invacom-qph-031-qph031-dss-circular-linear-ku-lnbf.htm , don't know where to buy
- There's a lot of DIY information in Russian how to make a linear LNB to work in round polarization and in both polarizations.

I'm not ready to post translation right now, but I will do it later if community need it
Main principal is you need to take a little piece of plastic, cut it with the scissors to make a rectangle width=diameter of a waveguide. Length is experimental, to work in round polarization is about 40mm, to work in both round and line polarizations - shorter, 5-20mm. Place it in the waveguide in angle 45 degrees. Pics you can find here _http://dream.altmaster.net/showthread.php?t=1469

[nev]

Re: The difference between a Linear and Circular LNB

My understanding is that the linear polarisation is preferred to circular because twice as many channels can be got into any particular frequency. Against that there is the small problem of having to adjust the angle of the LNB (skew) because horizontal isn't always horizontal and vertical isn't always vertcal.

[alfred_1]

Re: The difference between a Linear and Circular LNB

My understanding is that the linear polarisation is preferred to circular because twice as many channels can be got into any particular frequency. Against that there is the small problem of having to adjust the angle of the LNB (skew) because horizontal isn't always horizontal and vertical isn't always vertcal.

I am sorry nev but the reason of having to adjust the 'Skew' of the LNB isn't because of what you said but simply because you have to align your Dish exactly to the same horiz/vert/ postion as the Satellite in the sky.

When you set the skew (Polarity) on your LNB you are lining up your dish exactly to the same horizontal/vertical position as the satellite in the sky.

The satellites all lie in a curveture in the sky and so are at different heights. Ku satellites use Horizontal and Vertical liner polarization and so the skew has to match the (H/V) position of the satellite for optimum satellite signal strength/quality.

[alfred_1]

Re: The difference between a Linear and Circular LNB

@Satfinder

Exactly so.

Mine:
''When you set the skew (Polarity) on your LNB you are lining up your dish exactly to the same horizontal/vertical position as the satellite in the sky''.

Yours:

''Satellite appears to be tilted as viewed from Earth, this means the LNB has to be tilted to a similar angle so that it matches the geometry position of the satellite''.

[nev]

Re: The difference between a Linear and Circular LNB

All the explanations seem to me to be correct - just a different way of explaining the phenomenon. Easy if you live on the Greenwich meridien and are setting up to receive transmissions from Thor - skew is zero!

[peet000000]

Re: The difference between a Linear and Circular LNB

A linear LNB can be converted to circular by adding a teflon piece

[jonny2by4]

Re: The difference between a Linear and Circular LNB

Difference is if linear, it broadcasts Horizontal and Vertical,if circular, it broadcasts Right Circular and Left Circular.