LNBF polarization tilt NA to dss LNBs(Sats)?

[sv1000]

Its my understanding that all non-fta sats (dss) transmit using some sort of "circular" method and there is never a need for tilting a LNB (and nor can you and if you can, it won't improve signal strength or quality). Am I correct ?

The exception might be a specific Echostar satellite (not 6 or 7) that needs a KU band lnb and presumidly needs the lnb to be rotated ?

Same for what ever satellite a star-choice service in Canada uses ?

Am I wrong ?

[rainman]

no one of the echo star sats use a linear lnb while the others are circular.nothing much FTA on these sats anyway.

[wejones]

Originally Posted by sv1000

Its my understanding that all non-fta sats (dss) transmit using some sort of "circular" method and there is never a need for tilting a LNB (and nor can you and if you can, it won't improve signal strength or quality). Am I correct ?

The exception might be a specific Echostar satellite (not 6 or 7) that needs a KU band lnb and presumidly needs the lnb to be rotated ?

Same for what ever satellite a star-choice service in Canada uses ?

Am I wrong ?

This is an interesting question, to me at least. Yes, many of the DBS sats (I'm used to seeing the DSS term applied mainly to DTV, but DBS is a more generic term) use circular polarization, and most FTA signals are found on the linear polarized satellites. Linear polarization has the polarization of the signal either vertical or horizontal. The transmiting and receiving elements are usually just metal rods that are either horizontal or vertical, similar to TV antennas that have horizontal polarization and FM antennas that are usually vertical I think, like a car antenna. Circular polarization is basically a condition where the plane of polarization of the signal is rotating like a left or right handed spiral.
Most of the sats used by DTV are circular (exceptions being things like the channels on G3r which are transmitted on a linear satellite). Most of the sats used by Dishnet and Bell ExpressVu are circular, the Star Choice things are linear. Some of the Dishnet stuff is on linear sats, like the Echo-9 satellite is really the same satellite as IA13 and is a linear satellite. Also there are some sats, like AMC 15 and 16, which seem to be advertised as being capable of being either linear or circular.
The reason I find this interesting, is that to me, the signals put out by AMC15 and AMC16 do not seem to be pure circular to me. On most of the "pure" CP sats, when I use my linear feeds for reception, I can usually get some of the transponders, but usually only on one of the 2 polarizations, and as expected the signal strength and quality is reduced. However, on AMC15 and 16, I can get almost ALL the transponders on both polarities with my linear feed. My suspicion is that these hybrid satellites aren't really putting out pure circular polarization.
I've built and used a few types of CP antennas. There are some called quadrifilar helix that look like a twisted kitchen whisk and other antennas that look like cork-screws, that I think these put out pure CP, however there are some other antennas, that seem to simulate CP by phasing the signals into crossed linear elements. These can be made to be either circular or linear depending upon the way they are fed. My guess is that the hybrid satellites must use something like this. I don't think that these really produce "pure" circular polarization, but I might be wrong. Perhaps they should be called eliptical. In any event, you can switch between R and L by varying the H and V polarity of a linear feed. You can receive linear with a CP feed, and you can receive CP with a linear feed, but the problem is that you can't separate the polarities, so you get interferrence.
Re the comment above about a CP lnbf working at any angle.... in theory, yes, but I'm not positive that this is completely true. It may be my setup, but I have seen differences with respect to how well one of my CP lnbfs work depending on what orientation I place it at, however I haven't really experimented much. My guess is that it depends upon what technique is used within the lnbf to receive the CP, and how pure the original signal is. There are some feeds that receive CP by placing teflon slabs inside a linear feed. I don't consider this to be pure CP reception, and in my opinion, this type of CP feed would probably be dependent on it's orientation. I see them as just a way of increasing the signal from one polarity over the other polarity. However again, I've never really experimented with one of these, so I'm probably wrong. But right or wrong, I find this whole subject interesting, and some day, I intend to experiment a bit. And perhaps take apart one of those CP lnbfs to see what is inside.

[sv1000]

Thanks you guys for the replies. Being a noobie, I realize I am assuming all of Dish Networks satellites are Echostars. Please let me know if that is wrong. Below is an extract from FTA Manual.doc which lead me to believe you need a linear LNB for certain Dish sats. Anyone know this to be incorrect ?

" If, however, you want to tune into Dish Network’s 105 or 121 satellites, you will need a Ku-band linear LNB. This is because the signal type and frequency is different from the other Dish/BEV satellites."

[wejones]

Originally Posted by sv1000

Thanks you guys for the replies. Being a noobie, I realize I am assuming all of Dish Networks satellites are Echostars. Please let me know if that is wrong. Below is an extract from FTA Manual.doc which lead me to believe you need a linear LNB for certain Dish sats. Anyone know this to be incorrect ?

" If, however, you want to tune into Dish Network’s 105 or 121 satellites, you will need a Ku-band linear LNB. This is because the signal type and frequency is different from the other Dish/BEV satellites."

The 121 satellite is linear. The 105 satellite used to be linear, up until a month or two ago, but the new AMC-15 is *supposed* tp be one of those sats I mentioned that can be either linear or circular, so I'm not positive what it is. It's listed in Lyngsat as being linear, and it "seems" to be, as I can easily tune it with my linear feed, but I think that AMC-16 was listed as linear for a while too, and there was an argument about whether it was linear or circular. According to the AMC site, AMC 15 is supposed to be a twin of AMC-16.
My guess is that AMC15 is now linear because it is replacing a sat that was linear, and they don't want people to have to change hardware to receive it, whereas AMC16 went into a slot where they only had circular sats before, so they could go with circular on it.

[be236]

Hi,

Looking at a DTV dish/LNB which picks up CP sats, you can't "turn" the LNB any direction. It connects to the LNB arm in one direction, so I would think there's no concept of "skew" for CP sats...

As for AMC 16 (118.7w),I read on another site that that it is indeed some hybrid/special sat that broadcasts is some funky circular polarity format, but its frequency output values are typically linear frequencies. I tried to pick this signal (any signal really) when I aimed here and set my LO to 11250 (for CP) but in the Fortec Classic, it would not let me blind scan to lower freq ranges that belongs to LP transponders (an artificial SW limit I guess since it assumes no CP broadcast in this lower freq range)...

However I have heard reports of people with LP LNB can pick up those lower freq TPs but they signal strength is really low, like 40-50% and it's spotty at best.

I also saw a post for a "special" LNB that was designed to pick up those TPs for that particular sat... (heh)...

[wejones]

Originally Posted by be236

Hi,

Looking at a DTV dish/LNB which picks up CP sats, you can't "turn" the LNB any direction. It connects to the LNB arm in one direction, so I would think there's no concept of "skew" for CP sats...

In theory, if you are using a true CP feedhorn, no, but if you are using a modified linear feed to receive it, then yes, skew is important. I have one of my CP lnbfs attached on my big dish, and it sure seemed to me that it's performance changed when I rotated it, but I may have changed other things too.

Originally Posted by be236

As for AMC 16 (118.7w),I read on another site that that it is indeed some hybrid/special sat that broadcasts is some funky circular polarity format, but its frequency output values are typically linear frequencies. I tried to pick this signal (any signal really) when I aimed here and set my LO to 11250 (for CP) but in the Fortec Classic, it would not let me blind scan to lower freq ranges that belongs to LP transponders (an artificial SW limit I guess since it assumes no CP broadcast in this lower freq range)...

I assume you are talking about using your CP lnbf for this, and not your linear, because you don't change your LO freq to match the satellite, your LO freq must match your LNBF. {Ie I can pick up many CP transponders on my standard 10750 linear lnb, and I do this by just leaving the LO freq on 10750, since that's the LNB I'm using. But if you're using your CP lnbf, then 11250 is correct.}
But yes, receivers won't tune below 950 MHz, regardless of what band you are on. Ie this means they won't tune below 12200 if you're using a 11250 LO freq, and it won't tune below 11700 if you're using 10750, and won't tune above 4200 if you're using 5150. It will tune about 1000 MHz above the lower limit. Ie I think my Fortecs will tune up to about 12700 using 10750, but won't go below 11700.

Originally Posted by be236

However I have heard reports of people with LP LNB can pick up those lower freq TPs but they signal strength is really low, like 40-50% and it's spotty at best.

I also saw a post for a "special" LNB that was designed to pick up those TPs for that particular sat... (heh)...

I don't have any problem with the AMC16 sat using my linear LNB, however that's on my big dish, where polarity is variable, and it might have something to do with the particular feedhorn. I seem to remember that I didn't have quite as good luck with my 90CM dish, which has a non-variable polarity, ie only H/V and not between.

[be236]

The LNB that goes with DTV dish is CP and is fitted one way only, you cant turn anything on it.

[quote=wejones;37967] Ie this means they won't tune below 12200 if you're using a 11250 LO freq, and it won't tune below 11700 if you're using 10750, and won't tune above 4200 if you're using 5150. It will tune about 1000 MHz above the lower limit. Ie I think my Fortecs will tune up to about 12700 using 10750, but won't go below 11700.
[quote]

Yes, the above quote is what I am finding... when I hooked my my dtv/cp LNB to point at AMC 16 (118.7w) and set my matching LO to 11250, I tried to pick up the lower freqs listed in Lyngsat, but it would NOT let me go any lower than 12200 to get those TPs.

So, are you saying that instead I can use my 80cm dish and Linear LNB point to there and use LO of UNIV/10750 and try to pick up those freqs even though they are broadcast in this funky circular polarity fashion?

[wejones]

Originally Posted by be236

The LNB that goes with DTV dish is CP and is fitted one way only, you cant turn anything on it.
.........

So, are you saying that instead I can use my 80cm dish and Linear LNB point to there and use LO of UNIV/10750 and try to pick up those freqs even though they are broadcast in this funky circular polarity fashion?

Re the DTV lnbf, right, unless you rotate the whole dish, or take the lnbf off the DTV dish, which is what I did. You don't have to connect those things via the rectangular thing at the end, if you're mounting on another dish.

You should be able to pick up some of the AMC16 things (although I think they were all scrambled) with your 80CM. If it's a UNIV, just use the regular 9750/10600. My 10750 example was for a standare lnbf, not UNIV.
I think that with my big dish I locked nearly all the transponders using a linear feed, however if I remember right (it was several months ago), with the 90CM, I wasn't getting all the transponders. I blamed it on not being able to fine tune the polarity like I could with the polarotor.

[be236]

Ok, here's the deal. I got the Fortec Universal LNB from Sadoun here. I dont know what's the difference between Universal and Standard. I thought both are linear LNBs.

Anyways, as for 118w, there are two sats parked there, one at 118.7w and the other is 119w (basically almost on top of each other, so if you aim for one, you get both I suppose)... Both these sats are CP, right... and so, I was able to pick up a signal on 119w using my DTV LNB (CP) fine, but in my Classic menu, it wont let me get 118.7w since those CP transponders broadcast at lower freq range, typically used/reserved for linear freqs, under 12200.

So, in my Classic menu, when I use the Fortec LNB, I have to set it to UNIV LNB (not 10750, though that I may work as well), and then I can try to scan for those freqs under 12200 for 118.7 even though they are CP.... you say this should work, right?

Well, I'll try it out one of these days when I get some free time and it's not raining and cold outside...

[rainman]

Originally Posted by be236

Ok, here's the deal. I got the Fortec Universal LNB from Sadoun here. I dont know what's the difference between Universal and Standard. I thought both are linear LNBs.

Anyways, as for 118w, there are two sats parked there, one at 118.7w and the other is 119w (basically almost on top of each other, so if you aim for one, you get both I suppose)... Both these sats are CP, right... and so, I was able to pick up a signal on 119w using my DTV LNB (CP) fine, but in my Classic menu, it wont let me get 118.7w since those CP transponders broadcast at lower freq range, typically used/reserved for linear freqs, under 12200.

So, in my Classic menu, when I use the Fortec LNB, I have to set it to UNIV LNB (not 10750, though that I may work as well), and then I can try to scan for those freqs under 12200 for 118.7 even though they are CP.... you say this should work, right?

Well, I'll try it out one of these days when I get some free time and it's not raining and cold outside...

you set the universal lo to 9750 10600 the standard lo sets at 10750 the universal allows you to get the transponder freq below 11700.

[be236]

Ah, okay, so:

you set the universal lo to 9750 10600 the standard lo sets at 10750 the universal allows you to get the transponder freq below 11700.

This since I have UNIV LNB from Fortec, then I can get freqs undre 11700, but I dont see any sats or TPs that list in Lyngsat under 11700 for me to use this special feature... hmmm...

[satnutwillb]

Pas-9 ku has cubavision on it if you can reach that far.

[rainman]

Originally Posted by satnutwillb

Pas-9 ku has cubavision on it if you can reach that far.

also some channels on Nanuel satellite use a universal lnbf.if the beam is region 3 should be able to receive it.

[be236]

Oh, I see... no, I can't get anything east past 80w or so...

I wish more sats where on the western end, like 130-160-170w.. that'd be nice.. heheh.. lots of empty slots there..