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Fringe Reception General
Best receiver for fringe reception
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<blockquote data-quote="IanW" data-source="post: 660681" data-attributes="member: 176464"><p>Dovercat - your point about your Televes LNB matching your Televes antenna is well made, the feedhorn design should illuminate the antenna surface efficiently without 'seeing' beyond it ideally, to create a reasonable antenna pattern. </p><p></p><p>The old saying 'it's all in the twig' is so true. Good antenna designs minimise off-axis reception and deliver good x-pol (cross-polar) isolation, reducing interference. Reception is truly about C/NI (Carrier-to-Noise+Interference).</p><p></p><p>Likewise, your point about SCPC (Single Channel Per Carrier, ie under 6MS/s DVB-S) performance is very true, early tuner designs incorporated a SAW IF filter and/or Low-pass analogue filter ahead of the demodulator stage. The Nokia 9500/9600 has within it the original TV-COM Inc. (there's a name from history, 1994) tuner design card; it has these filters to assist the demodulator stage handle the full range from 2MS/s > 45MS/s.</p><p></p><p>I do wonder, if subsequent tuner designs rely too heavily on the digital domain filters to deliver demodulation performance. The 'zero-IF' designs may not handle strong carriers well at their input, when trying to select out a weaker carrier. I suspect they fall back on the inherent robustness of the DVB-S and now DVB-S2 modulation+FEC to reject unwanted mutual carriers, that's all well and good, but again it's C/N+I.</p><p></p><p>In the world of fringe reception, the weak wanted carrier can be amongst or alongside a forest of unwanted strong interferers which may have entered the antenna from the front or side, and both the wanted and unwanted can arrive at the same level into the demodulator stage. Every 0.5dB is precious.</p><p></p><p>Comparing real side-by-side receiver performance has to be done carefully, the same antenna+LNB, carrier, weather, day.</p><p></p><p>Happy 2010 everyone, 'let's hope it's a good one'.</p></blockquote><p></p>
[QUOTE="IanW, post: 660681, member: 176464"] Dovercat - your point about your Televes LNB matching your Televes antenna is well made, the feedhorn design should illuminate the antenna surface efficiently without 'seeing' beyond it ideally, to create a reasonable antenna pattern. The old saying 'it's all in the twig' is so true. Good antenna designs minimise off-axis reception and deliver good x-pol (cross-polar) isolation, reducing interference. Reception is truly about C/NI (Carrier-to-Noise+Interference). Likewise, your point about SCPC (Single Channel Per Carrier, ie under 6MS/s DVB-S) performance is very true, early tuner designs incorporated a SAW IF filter and/or Low-pass analogue filter ahead of the demodulator stage. The Nokia 9500/9600 has within it the original TV-COM Inc. (there's a name from history, 1994) tuner design card; it has these filters to assist the demodulator stage handle the full range from 2MS/s > 45MS/s. I do wonder, if subsequent tuner designs rely too heavily on the digital domain filters to deliver demodulation performance. The 'zero-IF' designs may not handle strong carriers well at their input, when trying to select out a weaker carrier. I suspect they fall back on the inherent robustness of the DVB-S and now DVB-S2 modulation+FEC to reject unwanted mutual carriers, that's all well and good, but again it's C/N+I. In the world of fringe reception, the weak wanted carrier can be amongst or alongside a forest of unwanted strong interferers which may have entered the antenna from the front or side, and both the wanted and unwanted can arrive at the same level into the demodulator stage. Every 0.5dB is precious. Comparing real side-by-side receiver performance has to be done carefully, the same antenna+LNB, carrier, weather, day. Happy 2010 everyone, 'let's hope it's a good one'. [/QUOTE]
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Best receiver for fringe reception
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