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Discussion Starter · #1 ·
Recently I bought a Sat C LNB on occasion. However it wasn't a kit - so it didn't include a combiner.


So I'm trying to make it work with a RadioShack hybrid 2-way splitter/combiner (product # 15-1141d).


It doesn't work very well.


If I connect both sat b and sat c cables into a combiner - then my receiver sees only sat b - sat c signal strength shows 0 on all xponders.


If I connect just a sat c into a combiner then my receiver sees all sat c xponders with decent signal strength but obviously doesnt' see even sat b transponders (odds are ok since they are on a 13v cable).


Is there something wrong about using a regular combiner for sat b/sat c?


All cables are OK, and sat c LNB is OK as well.


Whats the purpose of a combiner - just to split 18v 2-way, or there is more?


Maybe i just should buy a proper one? So, if anyone has an extra Sat b/Sat c combiner just lying around - PM me.


Thanks

Mike
 

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The combiner DirecTV shipped me is marked 18V / 22 kHz, if that's any help. Brand is NAS, part # SSC-1
 

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the combiner must have DC pass on both ports and be rated to at least 1500 Mhz. RS does not stock such a combiner. best bet is to find a retailer that sells channel master or monster cable accessories.
 

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The Sat C combiner is actually a high pass filter + combiner that allows the frequency shifted output of the Sat C transponders from the special C LNB to replace the regular lower channels of the Sat B signal. So a regular combiner wont work here, it has to be one of these special filter kinds made for this purpose.
 

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Yes. the kit supplied unit has a high pass filter. However in practice it is possible to use one without a high pass filter, though the noise figure will be higher ( in theory, a non filtered unit will have a slightly lower insertion loss ) . The monster cable unit seems to have a bandpass filter tuned for 950-2050 Mhz.
 

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You can't combine signals from a conventional LNB in the Sat B (119 degree) position and from a special Sat C LNB in the Sat C (110 degree), using a 950-2,000 power-passing splitter/combiner, because the Sat C LNB downshifts transponders 28, 30 and 32 to 8, 10, and 12, but the Sat B LNB is receiving DISH Network programming on those same transponder frequencies. The special Sat C combiner is a power passing diplexer with internal high-pass and low-pass filters, to make sure that the three low numbered transponders from Sat C and the eleven high numbered transponders from Sat B are not degraded by interference from each other.


Any product bearing the name Monster can be replaced by other products that do not charge a premium for the consumer confidence of buying a "brand-name". Any Sat/Ant diplexer is a 950Mz high-pass filter on its Sat side, and these can be bought for under $3.00 each if you need one, but such a filter is not used to combine Sat B and Sat C.


A Sat B/C diplexer low pass filter has to pass all frequencies under1,150Mz (upper edge of transponder 12) through its Sat C input, while blocking all frequencies starting at about 1,265Mz (lower edge of transponder 22). Conversely, the Sat B input has to pass the frequncies above 1,265mz while wiping out those below 1,150Mz. Because the guard band between the Sat B transponders and Sat C transponders is pretty wide (over 100Mz), the design of a diplexer with that gentle a roll off range is not very demanding and it can be manufactured cheaply, though I have never seen a price on one sold separately.
 
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