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Discussion Starter · #1 ·
How does a 4x4 multiswitch work (with a DTC-100) to select different transponders/birds ?


I suspect that my switch isn't working, maybe because it's not getting enough power/voltage drop too high in 90' of cable


below is some info I found on a 4x4 switch (appears similar to mine)

translation on "LHCP", "RHCP" , etc ???



a) 101° LHCP Selection

16.75 V to 21.0 V

b) 101° RHCP Selection

11.75 V to 14.0 V

c) 2nd Sat LHCP Selection

16.75 to 21.0 VDC, 22 kHz tone, continuous

d) 2nd Sat RHCP Selection

11.75 to 14.0 VDC, 22 kHz tone, continuous

Multiswitch LHCP/RHCP Selection Point with all tolerances, temp

14.8 Vdc ~ 15.5 Vdc
 

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The 22KHz tone is transmitted through the RF cable from the receiver to select which satellite slot is to be received - 101 or 119. There are two dual LNBs - one for 101, the other for 119. Each dual LNB literally has two electrically separate LNBs in a common housing. This allows for multiple receivers to operate independently off the multiswitch. The receiver also supplies two DC voltages to "switch" the LNB satellite signal reception polarity - either horizontal or vertical. This bit of trickery effectively allows doubling the number of potential channels available. When the RF cable is carrying a nominal 13 volts from the receiver (what you listed as 11.75 - 14 volts) the odd-numbered xponders are received. When the RF cable is carrying a nominal 18 volts from the receiver (what you listed as 16.75 - 21 volts) the even-numbered xponders are received. If you're using RG-6 RF cable, there's probably no difficulty in powering and switching the LNBs, even at 90'. But this length might be attenuating the 22Khz switching tone amplitude sufficiently that the multiswitch can't "hear" the command to switch to the other dual LNB. It might also be the case that the cable length is inteferring with the powering of the multiswitch. It gets its juice from the receiver, too. There are so-called "powered multiswitches". These take their power via a separate cable powered from a plug-in "wallwart" transformer-rectifier. If you had your dish professionally installed, though, it might be cheaper to have your installer run the diagnosis before you start buying what may be unnecessary equipment. You might have a defective multiswitch that's still under warranty for instance. RHCP & LHCP? Obviously right-hand and left-hand, but I don't have a clue about "CP". Suspect something to do with controlling power (Duhhh!...) to the two dual LNBs.




[This message has been edited by Ray H (edited 04-09-2001).]
 

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Ray,


Thanks for the explaining the operation of the multi-switch.


RCA sells two- and four-way splitters with DC-pass through, but with output-output DC isolation. From your description it sounds as if this splitter won't really work with the multi-switch, i.e., I'll need to run individual cables from the multi-switch to each STB (one for HDTV and one for Replay/Tivo recording).


Looks like I'll have to crawl under the house again...


Frank
 

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LHCP = Left Hand Circular Polorization

RHCP = RIght hand Circular Polorization


Satellite signals use circular polorization instead of horizontal and vertical because it penetrates the atmosphere with less distortion (though slightly more attenuation). Also, given the position of the satellite, there really is no "horizontal" or "vertical," from a terrestrial reference (one guy's horizontal is another guy's vertical...so to speak). So the put one set of elements at 90 degrees from another set of elements, then feed 'em out of phase to get the wavefront "spinning".


My old amateur radio satellite beams (VHF, 20 elements, 22 feet long / UHF - 40 elements, 18 feet long, both through 1/2" hardline with 26db pre-amps)did a great job for TV reception. . .reception from five or six states from the NorthWest side of Chicago.....


Those were the days....


FWIW


Scott
 
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