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Multi-receiver/TV systems - Domestic only
distrubution sky tv and digital /anolog
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<blockquote data-quote="spiney" data-source="post: 147953" data-attributes="member: 192438"><p>Sorry about the problem, I'll try and help.</p><p></p><p>Having looked it up, the labgear 8 way has rather high sat insertion loss, although that's not your problem!</p><p></p><p>It also has a rather low terr-to-sat isolation, 25 dB sounds a lot, but most multiswitches give 35 or 40dB isolation.</p><p></p><p>Yes, there's normally only 1 terr input, for 1-900 Mhz, the required terr bands being combined before that point, then they can be separately filtered off from sat i.f. inside the switch, to give the required bandpass frequency isolation.</p><p></p><p>Sounds like something on terr is overloading the sat section, possibly giving spurious products.</p><p></p><p>You're using sat cable, but what sort? Also, a purpose made combiner for fm/tv aerial? Hopefully, in which case, some frequency filtering should be present.</p><p></p><p>Unfortunately, a fm aerial - in particular - can pick up all sorts of uwanted things!</p><p></p><p>First, determine which aerial causes the problem. Leave terr in, but disconnect fm and tv in turn, does satellite then come back with either out?</p><p></p><p>Go through the UHF bands on tv, look for interference on particular channels. Also on fm radio, anything between channels?</p><p></p><p>When you have all terrestrial, then what happens to sat "signal quality"?</p><p></p><p>That's a start ....</p><p></p><p>(added) more stuff to try ......</p><p></p><p>I see the labgear has built in attenuators. WIth terr connected, and sat polarities at max level, try slowly reducing the terr level, at some point does sat start working again?</p><p></p><p>I've noticed you also posted, just below, about analogue interference - on UHF signal out of a Sky receiver - suggesting there's a problem with the analogue distrinution. So, I'd expect "patterning" - clearly visible across the unused channels - on any analogue tv sets connected to the multiswitch distribution (with the terr tv aerial in!), is that what happens?</p><p></p><p>I'd never heard of Labgear multiswitches before this (but seen most other sorts), and unfortunately it turns out they have rather low terr/sat isolation (in my opinion, unacceptably low!). 15 dB difference doesn't sound much, but remember it's really 30 times, a huge amount!</p><p></p><p>Anyway, let's try and get some initial clues as to what's happening, then "close in" on the exact problem, keep fingers crossed ......</p></blockquote><p></p>
[QUOTE="spiney, post: 147953, member: 192438"] Sorry about the problem, I'll try and help. Having looked it up, the labgear 8 way has rather high sat insertion loss, although that's not your problem! It also has a rather low terr-to-sat isolation, 25 dB sounds a lot, but most multiswitches give 35 or 40dB isolation. Yes, there's normally only 1 terr input, for 1-900 Mhz, the required terr bands being combined before that point, then they can be separately filtered off from sat i.f. inside the switch, to give the required bandpass frequency isolation. Sounds like something on terr is overloading the sat section, possibly giving spurious products. You're using sat cable, but what sort? Also, a purpose made combiner for fm/tv aerial? Hopefully, in which case, some frequency filtering should be present. Unfortunately, a fm aerial - in particular - can pick up all sorts of uwanted things! First, determine which aerial causes the problem. Leave terr in, but disconnect fm and tv in turn, does satellite then come back with either out? Go through the UHF bands on tv, look for interference on particular channels. Also on fm radio, anything between channels? When you have all terrestrial, then what happens to sat "signal quality"? That's a start .... (added) more stuff to try ...... I see the labgear has built in attenuators. WIth terr connected, and sat polarities at max level, try slowly reducing the terr level, at some point does sat start working again? I've noticed you also posted, just below, about analogue interference - on UHF signal out of a Sky receiver - suggesting there's a problem with the analogue distrinution. So, I'd expect "patterning" - clearly visible across the unused channels - on any analogue tv sets connected to the multiswitch distribution (with the terr tv aerial in!), is that what happens? I'd never heard of Labgear multiswitches before this (but seen most other sorts), and unfortunately it turns out they have rather low terr/sat isolation (in my opinion, unacceptably low!). 15 dB difference doesn't sound much, but remember it's really 30 times, a huge amount! Anyway, let's try and get some initial clues as to what's happening, then "close in" on the exact problem, keep fingers crossed ...... [/QUOTE]
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distrubution sky tv and digital /anolog
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