Archived from groups: alt.video.ptv.tivo (
More info?)
DanR wrote:
> Dave Platt wrote:
>
>>>I currently have a Dual LNB setup. I have 2 lines coming into my house
>>>going into a multiswitch. 2 lines going into my Tivo, the other into
>>>another room.
>>>Can I add another multiswitch to the line that's in my other room to
>>>make that 2 lines as well? Or can you not re-split a line that is coming
>>>out of a splitter?
>>
>>You can usually daisy-chain one multiswitch off of another
>>(multi-satellite setups can be tricky, though).
>>
>>In order to do it, you must have *two* free ports on the upstream
>>multiswitch (the one closer to the dish). Connect these to the two
>>"LNB" inputs on the second multiswitch, and then connect a bunch of
>>downstream devices to the output ports on the second multiswitch.
>>
>>
>>>How is the multi switch diff't than a basic coaxial splitter?
>>
>>It's a much more sophisticated device, because it has to be.
>>
>>An LNB outputs a whole bunch of satellite signals at once - it's a
>>"Low Noise Blockconverter" which shifts a whole range of the microwave
>>spectrum down to a lower frequency range (one which can go over coax
>>without being lost). There are actually two sets of signals being
>>transmitted by the satellite in each frequency range - they have
>>opposite polarization senses (one set is "left-hand circular
>>polarized" and the other is "right-hand circular polarized"). The LNB
>>receives, and block-converts either the LHCP set, or the RHCP set, at
>>any given moment. Which set it receives and converts, depends on the
>>DC power voltage being fed up to it via the coax cable (it's either 13
>>or 18 volts, nominal).
>>
>>A single receiver can use a single LNB, and switch the LNB between
>>LHCP and RHCP signals as it wishes, depending on which transponder
>>it wants to receive.
>>
>>You can't put two receivers (or tuners) on a single cable to a single
>>LNB, because a lot of the time they'll want signals of different
>>polarization sense, they'll [try to] send conflicting DC voltages up
>>the coax, they'll fight, and one of them (at least) will lose and will
>>not get the signal it wants.
>>
>>So, to use two tuners (or two single-tuner receivers) you need two
>>separate LNBs (or a dual LNB in a single enclosure).
>>
>>To run three or more tuners from two LNBs (or a dual LNB) you play
>>games - you use a multiswitch. The 'switch always feeds 13 volts up
>>to one LNB and 18 volts to the other, so the LNBs themselves are
>>locked on to the same polarizations. The 'switch then "listens" to
>>the DC voltage it receives from each tuner, and selects one or the
>>other LNB's signal to feed down to the tuner.
>>
>>Hence, you can daisy-chain two multiswitches (usually). The
>>"upstream" switch (near the dish) looks like a pair of LNBs to the
>>"downstream" LNB, and the "downstream" LNB looks like a pair of
>>tuners/receivers to two of the ports on the "upstream" LNB.
>
>
> Great explanation Dave!
>
>
Wow.Yes, great explanation thanks.
My current switch has 2 lnb inputs, 3 sat outputs. Could I just replace
it with a switch (radio shack has'em) that has 4 outputs? This way I get
dual tuner in each room.
/www.radagast.org/jade-warrior
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