| Author |
Message |
Richard L
Guest
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 Posted:
Sun Nov 06, 2005 5:08 pm Post subject:
Polarity and C-band LNB |
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A friend abroad is unsuccessfully trying to pick up Russian C-band
stations from 40deg E using a Humax receiver and a Eurostar ESCE-870
LNB. His receiver settings all appear to be correct, including the
local oscillator frequency, but he can't find any signal at all.
Unfortunately I can't find a data sheet on the LNB, and I don't know
what the conventions are in C-band equipment.
The channel of interest has right-hand circular polarization, and the
LNB was sold as suitable for this particular satellite (in fact,
Google finds several pages of references to it in Russian). However,
what I haven't been able to discover is whether the polarization is
switched by the same 14V/18V levels as Ku-band LNBs are -- and, if so,
which polarities correspond to the H and V settings of the Humax
receiver. Can anyone help?
The receiver is presumably OK because it works with Ku-band. It also
has a mysterious 'Auto' polarization option (presumably it tries
both) but this has so far failed to find anything.
--
Richard L. |
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R. Mark Clayton
Guest
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| Posted:
Sun Nov 06, 2005 10:39 pm Post subject:
Re: Polarity and C-band LNB |
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"Richard L" <usenet@nowirelessspam.demon.co.uk> wrote in message
news:e8c4afc54d.usenet@wireless.demon.co.uk...
| Quote: | In message <cofsm158fqpi02fpl4biir9oa9ut8s8e0t@4ax.com
Charles Ellson <charles@ellson.demon.co.uk> wrote:
What size dish is he using ? C-band tends to use somewhat bigger
dishes than Ku-band.
90cm, but the signal strength shown on the footprint map is 48dBW for
this transponder, which ought to allow him to get by with much less.
--
Richard L.
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IMHO way too small, because it is not many wavelengths across in C-Band. |
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Charles Ellson
Guest
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| Posted:
Sun Nov 06, 2005 11:38 pm Post subject:
Re: Polarity and C-band LNB |
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On Sun, 06 Nov 2005 11:59:48 GMT, Richard L
<usenet@nowirelessspam.demon.co.uk> wrote:
| Quote: | A friend abroad is unsuccessfully trying to pick up Russian C-band
stations from 40deg E using a Humax receiver and a Eurostar ESCE-870
LNB. His receiver settings all appear to be correct, including the
local oscillator frequency, but he can't find any signal at all.
Unfortunately I can't find a data sheet on the LNB, and I don't know
what the conventions are in C-band equipment.
The channel of interest has right-hand circular polarization, and the
LNB was sold as suitable for this particular satellite (in fact,
Google finds several pages of references to it in Russian). However,
what I haven't been able to discover is whether the polarization is
switched by the same 14V/18V levels as Ku-band LNBs are -- and, if so,
which polarities correspond to the H and V settings of the Humax
receiver. Can anyone help?
The receiver is presumably OK because it works with Ku-band. It also
has a mysterious 'Auto' polarization option (presumably it tries
both) but this has so far failed to find anything.
|
What size dish is he using ? C-band tends to use somewhat bigger
dishes than Ku-band.
--
_______
+---------------------------------------------------+ |\\ //|
| Charles Ellson: charles@e11son.demon.co.uk | | \\ // |
+---------------------------------------------------+ | > < |
| // \\ |
Alba gu brath |//___\\| |
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Richard L
Guest
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| Posted:
Mon Nov 07, 2005 12:38 am Post subject:
Re: Polarity and C-band LNB |
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In message <cofsm158fqpi02fpl4biir9oa9ut8s8e0t@4ax.com>
Charles Ellson <charles@ellson.demon.co.uk> wrote:
| Quote: | What size dish is he using ? C-band tends to use somewhat bigger
dishes than Ku-band.
|
90cm, but the signal strength shown on the footprint map is 48dBW for
this transponder, which ought to allow him to get by with much less.
--
Richard L. |
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boskar
Guest
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| Posted:
Mon Nov 07, 2005 1:08 am Post subject:
Re: Polarity and C-band LNB |
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Think there must be a big big big misunderstanding here. The lnb you
refer to works on 11.7ghz to 12.5 ghz which we call the DBS
band.Earlier used by the Tele-X satellite and the Marco Polo satellites
as the most known satellites. C-Band lnb has 3.4ghz to 4.2ghz. To
receive the satellite on 40degrees east and most of the C-Band channels
, my guess will be a 1.8m dish and a suitable C-Band lnb which can be
both cirkuar (changing polarization with external polarizer or a
dielectric plate inserted in the feed), or a linear lnb changing
polarisation with volt just like a universal lnb. |
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boskar
Guest
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| Posted:
Mon Nov 07, 2005 1:08 am Post subject:
Re: Polarity and C-band LNB |
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Sorry, a search tells me that there really is a C-Band lnb with that
name and that it is linear with volt swithing. But received signals
will be weaker because its linear. You can gain the signal by inserting
a 4mm thick dielectric plate in the feed in 45 degrees from those small
antennas in the lnb. dielectric plate should be a teflonplate. You will
gain the signal with ca 50% in some cases. The satellite sends as its
said, cirkular. |
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HJK
Guest
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| Posted:
Mon Nov 07, 2005 1:08 am Post subject:
Re: Polarity and C-band LNB |
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"Richard L" <usenet@nowirelessspam.demon.co.uk> skrev i melding
news:e8c4afc54d.usenet@wireless.demon.co.uk...
| Quote: | In message <cofsm158fqpi02fpl4biir9oa9ut8s8e0t@4ax.com
Charles Ellson <charles@ellson.demon.co.uk> wrote:
What size dish is he using ? C-band tends to use somewhat bigger
dishes than Ku-band.
90cm, but the signal strength shown on the footprint map is 48dBW for
this transponder, which ought to allow him to get by with much less.
--
Richard L.
|
The antennasize sounds wery small. Be aware that antennagain will be almost
10dB less on C-band compared
to Ku-band. |
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Richard L
Guest
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| Posted:
Tue Nov 08, 2005 1:08 am Post subject:
Re: Polarity and C-band LNB |
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In message <1131320409.171248.322750@g44g2000cwa.googlegroups.com>
"boskar" <boskar@bbnett.no> wrote:
| Quote: | Sorry, a search tells me that there really is a C-Band lnb with that
name and that it is linear with volt swithing. But received signals
will be weaker because its linear. You can gain the signal by inserting
a 4mm thick dielectric plate in the feed in 45 degrees from those small
antennas in the lnb. dielectric plate should be a teflonplate. You will
gain the signal with ca 50% in some cases. The satellite sends as its
said, cirkular.
|
Thank you, Boskar, that's most helpful. I'll pass it on to him.
--
Richard L. |
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Richard L
Guest
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| Posted:
Wed Nov 09, 2005 1:08 am Post subject:
Re: Polarity and C-band LNB |
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In message <dkm0mo$309$1@nwrdmz01.dmz.ncs.ea.ibs-infra.bt.com>
"R. Mark Clayton" <nospamclayton@btinternet.com> wrote:
| Quote: |
"Richard L" <usenet@nowirelessspam.demon.co.uk> wrote in message
news:e8c4afc54d.usenet@wireless.demon.co.uk...
In message <cofsm158fqpi02fpl4biir9oa9ut8s8e0t@4ax.com
Charles Ellson <charles@ellson.demon.co.uk> wrote:
What size dish is he using ? C-band tends to use somewhat bigger
dishes than Ku-band.
90cm, but the signal strength shown on the footprint map is 48dBW for
this transponder, which ought to allow him to get by with much less.
IMHO way too small, because it is not many wavelengths across in C-Band.
|
Can't lay my hands on it now, but somewhere on the Web a while ago I
found a nice table of dish sizes for various power levels, and this
appeared to show that a 60cm dish would be adequate for 48dBW in
C-band. Allowing 3dB loss for a linear-polarized LNB, 90cm still ought
to do the job.
--
Richard L. |
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