How am I getting this?

[tiredold]

While resetting my KU dish, I found QuetzSat 1 at 77. I scanned and got these signals. My qusetion is how. I have a linear LNB yet these are listed as circular. Is it that their signal is so strong that they are picked up. Would I be able to get other circular signals? Anyone experience this? Thanks in advance.

	TV Méxiquense		7.9	Mexdoomer 231004
TV Méxiquense		MPEG-2/HD	51 Spa
AMX Noticias		MPEG-2/SD	81 Spa
AMX Noticias +1		MPEG-2/SD	91 Spa
TV Méxiquense		MPEG-4/HD	67 Spa

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12276 R
tp 5
Conus​

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DVB-S2
8PSK
10500
3/4​

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1​

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49​

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2​

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79​

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3​

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89​

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4​

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65​

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[Titanium]

There is an approximate 3dB attenuation when receiving circular polarity on a linear polarity feed and visa versa. Many satellite signals are strong enough to be attenuated 3dB and still decode. Just depends on the reflector size and if optimized.

Will likely duplicate each transponder and service on both polarities lists within the band pass frequency range of the LNBF.

 

[tiredold]

Thete is an approximate 3dB attenuation when receiving circular polarity on a linear polarity feed and visa versa. Many satellite signals are strong enough to be attenuated 3dB and still decode. Just depends on the reflector size and if optimized.

Will likely duplicate each transponder and service on both polarities lists within the band pass frequency range of the LNBF.

Thank you. That is what I thought.

 

[arlo]

Did you read my freak-out when my dish had a sheet of ice on the lower half and circular sats were coming in strong?
Ice melted, signals back to way low.
I just peaked signal on 40.5W and am getting 6.5-11 dB. Blind scanned (no depolarizer) and added the results to my satellites.xml.
Polarities are mixed with L,R & H,V. But what makes the difference is that +/- 1 MHz and just a little variance in sr.

 

[cyberham]

There is an approximate 3dB attenuation when receiving circular polarity on a linear polarity feed and visa versa. Many satellite signals are strong enough to be attenuated 3dB and still decode.
.

I tested this a few weeks back on 77W using my 41" dish. With a circular LNB: 14+ dB. With linear: About 12 dB. It's a strong tp!

https://www.satelliteguys.us/xen/threads/mexiquense-on-77w-ku-quetzsat.403198/post-4953332

 

[Brct203]

there's the 3dB attenuation, but a strong signal is not enough in itself. Think of circular as diagonal - a mix of H and V. and from the perspective of circular signals, think of linear also as a mix of L and R.

So when you have a strong transponder that is circular, by using a linear LNBF, you get some of the signal, but not all of it, hence the 3dB attenuation.

However, let's say that was a Right-hand circular. Now let's change it to Left hand circular. The result is similar, you get part of the signal, with attenuation. If it's strong, it still works fine.

Now let's look at a crowded satellite, where most/all transponders are in use. They are usually alternating L/R, but in terms of frequency alone, they overlap. It works fine with the proper LNBF as it filters out the opposite polarity. But back to the example I discussed above, let's say there's a L signal and a R signal, with some overlap in frequency spectrum used by the transponders. The linear LNBF will pickup signal from BOTH trsnponders, and will mix them up, resulting in a mess and no reception.

So sometimes we are able to pick up circular signals with a linear LNBF and some thimes it just won't work... It will work only if there's no overlapping signal in the opposite polarity