Felix Hi, Fwd'd mail inlined. Reply from one of the major broadcasters over here in the persian Gulf region. http://www.adduniverse.com So as the reply states, i was right additionally, alongwith Felix conclusion of the C band inversion. In reality, we therefore have inversion due to * I/Q wiring * Flo > Frf Does anybody have any different thoughts ? Regards, Manu -------- Original Message -------- Subject: RE: Some thoughts and questions Date: Sun, 30 Sep 2007 09:56:53 +0400 From: Shaji Joseph <shaji@xxxxxx> To: Manu Abraham <abraham.manu@xxxxxxxxx> References: <46FE059F.1010907@xxxxxxxxx> <46FE12D7.2080202@xxxxxxxxxxxx> <46FE1C02.5040703@xxxxxxxxx> <46FE1F7C.40107@xxxxxxxxxxxx> <46FE256D.9070704@xxxxxxxxx> <46FE26F8.4060800@xxxxxxxxxxxx> <46FE2EB6.2000403@xxxxxxxxx> <46FE308B.1020401@xxxxxxxxxxxx> <46FE3806.4080206@xxxxxxxxx> In my understanding, Spectral inversion was done only on C band analogue transmissions. And receivers used to have an option to select inversion ON or OFF. Regards Shaji Joseph -----Original Message----- From: Manu Abraham [mailto:abraham.manu@xxxxxxxxx] Sent: 29 September 2007 15:33 To: Shaji Joseph Cc: Felix Domke Subject: Re: Some thoughts and questions Dear Shaji, Can you please enlighten us whether "broadcasters are required to send non-inverted signals" as described in the rest of the mail, in case you have any idea on the same. (We are talking about QPSK modulation/demodulation, according to college books, as implemented by a broadcaster) Regards, Manu Felix Domke wrote: > Hi, > >>>>>>> - Inversion might happen on up- and downconversion, depending on what >>>>>>> frequency situation you have. >>>>>>> - The SatelliteDeliverySystemDescriptor does not specify Inversion. >>>>>> AFAICS, Inversion isn't a part of the transport. >>>>> Why not? It's part of it like the frequency, isn't it? >>>> What i meant is that it does not depend on the transport, but the hardware. >>>> LNB + tuner <-> demod wiring >>>> Whereas frequency is not. >>> Some transponders have an inversed frequency spectrum already when >>> broadcasted (before downconversion). >>> There is no way for the broadcaster to specify this. >> What do you mean by a inverted spectrum when broadcast ? >> AFAICS, Inversion happens after there is a Phase shift to extract the I and Q signals > Swapping I/Q is *one* way to create spectral inversion. Just inverting > the spectrum is (obviosly) another one, and can happen on the > (non-complex) modulated signal as well. Just mix it with another > frequency and take the lower sideband. > > It's the same thing which happens in a C-Band downconversion - it can > also happen in the upconversion. > > I don't know if broadcasters are required to send non-inverted signals. > I just know (read: remember) that some do. I might be wrong, so second > opinions are welcome. > > Again, I'm not a frontend guy. Maybe somebody with broadcasting > experiences can tell us more here. > > Felix > ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ ______________________________________________________________________ Arab Digital Distribution DISCLAIMER: This Email and its attachments may contain information that is confidential and may be subject to legal privilege and copyright. If you are not the intended recipient you may not peruse, use, disclose, distribute, copy or retain this message. For more information about us visit www.art-tv.net or www.pehlatv.net or www.firstnettv.net This email has been scanned by the MessageLabs Email Security System _______________________________________________ linux-dvb mailing list linux-dvb@xxxxxxxxxxx http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
