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  1. #1
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    Default Circular/linear Polarity Problems


    Yes, as many rdi'ers know , putting a teflon dielectic plate in the feedhorn solves most reception problems with circular polarity satellites .
    However there is a price to pay and a BIG price if your dish is large and the feedhorn difficult to access.
    While it solves the problems for circular it causes problems for linear...namely weakens considerably the signal of linear channels !

    MY DREAM/THE IDEAL SOLUTION not yet invented ..an electronic device in the feedhorn, set in the menu , which has the same effect as the teflon plate which switches on and off AUTOMATICALLY according the the sat being watched in much the same way as v/h 0/12v 0/22H. does .

    Even if that were not possible a MANUAL electronic switch would be fine.
    ANY INVENTORS OUT THERE

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    Default

    I think there is already a linear & circular compatiable feedhorn in the market. But I forgot its name. But when I used the Yuri lnb it received both linear & circular signals without teflon! But other feedhorns refused the same

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    Default

    Quote Originally Posted by lnb15k View Post
    I think there is already a linear & circular compatiable feedhorn in the market. But I forgot its name. But when I used the Yuri lnb it received both linear & circular signals without teflon! But other feedhorns refused the same

    Hi Friend ,

    What's this Yuri lnb is it some different LNB.

  4. #4
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    Default

    @bangalore

    No. The company name is Yuri. They are famous for selling Ku + C combained.

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    Default

    Any LNB should be capable of receiving circular signal. If your dish is big enough you won't even need a plate.
    But C-BAND is right, it would be an interesting gadget. I would also like to see a skew adjuster (like the old Chapparal LNB's)

  6. #6
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    Default

    I have also tested the Teflon Dielectric plate on a linear Feedhorn/lnb and not happy with the results I've got.
    However I bought a clone copy of the ADL Circular/Linear Feedhorn and was happy with the results I'm getting compare to a dielectric plate.


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    Default

    One way round the problem is a twin C.band LNB. These consist of a pair of LNB's connected via a figure 8, scalar ring. Tune one LNB for H and V and add a dilectic plate for the circular stuff, in the other
    Fortunatly very few satellites use circular on C bands these days, Intelsat 701, comes to mind. In the old analogue days of Intersputnik, Statsionar and Gorizont all used circular.
    But at the end of the day nothing beats a dedicated Circular LNB
    regards from OZ bassett

  8. #8
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    Quote Originally Posted by Aldeto View Post
    I have also tested the Teflon Dielectric plate on a linear Feedhorn/lnb and not happy with the results I've got.
    However I bought a clone copy of the ADL Circular/Linear Feedhorn and was happy with the results I'm getting compare to a dielectric plate.

    Although the big problem nowadays is getting weak KU signals as C band is never a serious problem in SE Asia can you please let us know who sells the interesting circular/linear feedhorn you illustrated, its make, price and country where available.
    Many thanks

  9. #9
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    Quote Originally Posted by weirdo View Post
    Any LNB should be capable of receiving circular signal. If your dish is big enough you won't even need a plate.
    But C-BAND is right, it would be an interesting gadget. I would also like to see a skew adjuster (like the old Chapparal LNB's)
    Hi rdi'ers
    Here's the latest MANUAL skew adjuster f.....or KU band

    DESCRIPTION "Feehorn boss which holds the feed and allows for rotation for setting polarity

    See it on : http://www.satellitesuperstore.com/feedhorn.htm

    You still have to access the fedhorn which is quite a job if you've a large dish high up !

  10. #10
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    Quote Originally Posted by lnb15k View Post
    I think there is already a linear & circular compatiable feedhorn in the market. But I forgot its name. But when I used the Yuri lnb it received both linear & circular signals without teflon! But other feedhorns refused the same
    Hi Friend,

    How Much is the Price of Yuri lnb and What Dish size you used to receive Circular signal and which satellite.

    Can I use this with my 6 feet solid dish for Ku band & c band combine.

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    Quote Originally Posted by C-BAND View Post
    Although the big problem nowadays is getting weak KU signals as C band is never a serious problem in SE Asia can you please let us know who sells the interesting circular/linear feedhorn you illustrated, its make, price and country where available.
    Many thanks
    It's probably an ADL, but remember it's only an orthomode feed horn, NO LNB's they bolt on side and end of the unit in the square sections.

    Years ago you would pay a lot of money for such a unit, now due to electronic switching , there not used all that much , BUT if your receiver is not equiped with servo switching, you can forget one, unless you can find an old analogue receiver, to power the servo.

    Where to get,, These days only one person in the Pacific area , and he's not cheap. Av-comm in north sydney. http://www.avcomm.com.au

    The model shown will cost you $330.00 plus the price of the LNB's and freight
    regards from OZ bassett

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    Quote Originally Posted by C-BAND View Post
    Hi rdi'ers
    Here's the latest MANUAL skew adjuster f.....or KU band

    You still have to access the fedhorn which is quite a job if you've a large dish high up !
    Exactly, would be nice if they had a (cheap) motorised one.

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    Quote Originally Posted by Bangalore View Post
    Hi Friend,

    How Much is the Price of Yuri lnb and What Dish size you used to receive Circular signal and which satellite.

    Can I use this with my 6 feet solid dish for Ku band & c band combine.
    the YURI is produced by the ADITRON Company of SINGAPORE.
    You can buy direct . Their email address is [email protected]
    They are a company of the very highest integrity...GUARANTEED.

  14. #14
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    Quote Originally Posted by Bangalore View Post
    Hi Friend,

    How Much is the Price of Yuri lnb and What Dish size you used to receive Circular signal and which satellite.

    Can I use this with my 6 feet solid dish for Ku band & c band combine.
    You can use Yuri instead of getting a prime focus ku lnbf. So you can get both Ku and C band easily from your dish I bought that for Rs.1800 (some time back it was 1400). As C Band said you first contact them directly so that the price will be lesser or else you can buy from a local shop near you. Also share the information with us.

  15. #15
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    Default


    Dear friends,

    Advantages of Circular Polarization



    Reflectivity: Radio signals are reflected or absorbed depending on the material they come in contact with. Because linear polarized antennas are able to “attack” the problem in only one plane, if the reflecting surface does not reflect the signal precisely in the same plane, that signal strength will be lost. Since circular polarized antennas send and receive in all planes, the signal strength is not lost, but is transferred to a different plane and are still utilized.

    Absorption: As stated above, radio signal can be absorbed depending on the material they come in contact with. Different materials absorb the signal from different planes. As a result, circular polarized antennas give you a higher probability of a successful link because it is transmitting on all planes.

    Phasing Issues: High-frequency systems (i.e. 2.4 GHz and higher) that use linear polarization typically require a clear line-of-sight path between the two points in order to operate effectively. Such systems have difficulty penetrating obstructions due to reflected signals, which weaken the propagating signal. Reflected linear signals return to the propagating antenna in the opposite phase, thereby weakening the propagating signal. Conversely, circularly-polarized systems also incur reflected signals, but the reflected signal is returned in the opposite orientation, largely avoiding conflict with the propagating signal. The result is that circularly-polarized signals are much better at penetrating and bending around obstructions.

    Multi-path: Multi-path is caused when the primary signal and the reflected signal reach a receiver at nearly the same time. This creates a an “out of phase” problem. The receiving radio must spend its resources to distinguish, sort out, and process the proper signal, thus degrading performance and speed. Linear Polarized antennas are more susceptible to multi-path due to increased possibility of reflection. Out of phase radios can cause dead-spots, decreased throughput, distance issues and reduce overall performance in a 2.4 Ghz system.

    Inclement Weather: Rain and snow cause a microcosm of conditions explained above (i.e. reflectivity, absorption, phasing, multi-path and line of sight) Circular polarization is more resistant to signal degradation due to inclement weather conditions for all the reason stated above.

    Line-of-Sight: When a line-of-sight path is impaired by light obstructions (i.e. foliage* or small buildings), circular polarization is much more effective than linear polarization for establishing and maintaining communication links.

    SOURCE : http://www.wirelessnetworkproducts.c...S&Category=762


    ALL THE BEST
    Megahertzpark

 

 

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