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Topic:
DSS Signal Splitter - Technical question on splitting (help!)...
This thread has 9 replies. Displaying all posts.
Post 1 made on Monday March 18, 2002 at 11:34
jfetter
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OK, I know what a multi-switch is, I know what a diplexer is, I am very familiar with the method for splitting a dual LNB into 4, 6, 8, etc feeds. My problem;

I currently have a house pre-wired with 2 RG-6 and 2 CAT5 feeds to each Multimedia outlet. My Theater uses one RG-6 feed for Satellite and the other to broadcast the Satellite and DVD signals (via a 2 channel modulator) throughout the rest of the house. I do have other satellite receivers in some rooms but this offers a nice way to get Satellite TV and DVD to all TV's. Since I looped CAT5 throughout the house and put an IR receiver in the ceiling (centered between the whole house audio speakers in each room), I use it to route IR commands to the Theater where 12 emitters output the IR commands to all the Theater components making controlling everything possible.

I just purchased an UltimateTV unit (Sony SAT-W60) and definitely want to place it in the Theater. My problem is, with only 2 RG-6 feeds, I am one short if I want to use both internal UltimateTV tuners AND continue to broadcast the 2 modulated channels throughout the house. I have looked into Audio/Video over CAT5 and other solutions and here is my question. Can I SPLIT the "A" feed from the Satellite already coming in on one RG-6 and feed it into both UltimateTV inputs?

I am thinking the "A" and "B" signals are somehow combined and re-split in a normal multi-switch and this works because both are recombined or some other signal modification is made before being split into more feeds. I would love to just split the signal (using a regular 2GHz signal splitter) now but I am afraid of harming the UltimateTV. Does anyone know exactly how a dual LNB is split into 4 and if both "A" and "B" inputs MUST be used? What if I put another Terk 3 into 4 multiswitch in my theater and just fed in the one SAT "A" and then took 2 outputs from the back? Should 2 of the 4 outs works???

You see my dilema. If I don't come up with a way to split the signal in the Theater, I am left with the job of running a new RG-6 through the wall up to a Terk 3 into 4 splitter at the Dish (not far or hard since my Theater is on an outside wall at ground level, just not my ideal solution)...

Thank you in advance for your help...

Jfetter
OP | Post 2 made on Monday March 18, 2002 at 12:32
jfetter
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OK, this seems simple but could I use 2 diplexers, one at my Gateway Hub and the other in the Theater to both bring in the second Satellite feed (from the Gateway Hub to the Theater)AND distribute the 2 modulated channels throughout the house (from the Theater to the Gateway Hub to be distributed throughout the house)? Seems I might have answered my own question assuming someone can confirm...

Jfetter
Post 3 made on Tuesday March 19, 2002 at 02:19
Larry Fine
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To explain how a multiswitch works, and why splitting one (the A) cable won't work:

With a normal single receiver system, and a single LNB, the receiver sends a DC voltage (14v or 18v) up the coax to switch the LNB from even to odd channels. This is necessary because even channels are polarized either clockwise or counterclockwise (I forget which), and the odd ones are polarized the other way. This allows more channels within a given bandwidth.

When you add a second receiver, you need a dual LNB, so each receiver can independently select channels. This setup behaves exactly as if there were two separate dishes. Remember, each receiver sends a DC voltage which corresponds with the desired channel, so either cable can have either voltage on it at any moment.


However, with three or more receivers, since there are only two coaxes, and there can't be three different receivers trying to send the DC voltages on two cables, you need a multiswitch, which does several things:

First, it "locks" each element within the dual LNB to one polarization, by always sending 14v up one coax cable, and 18v up the other, so from now on, one cable carries only even channels and the other only odd.

Next, it switches each receiver from one of the LNB elements to the other. There is a relay or transistorized switch for each output of the multiswitch that senses the DC voltage at that output (hence the term 'multiswitch') and connects that output to either cable A or B. If all receivers happen to be tuned to even channels, for example, then they're all receiving their signals down the same coax from the dish.

Note that dual-tuner receivers, such as my Philips DSR6000Rs, require two multiswitch outputs and two cable runs, just as if they were two separate receivers. The output from a dual-tuner receiver, however, is a single cable, and the receiver acts like it has an A/B switch in it somewhere.

Actually, an A/B/C switch would be more appropriate for a dual-tuner TiVo like mine, since you can watch a prevoiusly-recorded program while recording two, or watch either tuner's program.


So, to answer your question, a dual-tuner receiver must have two feeds. It looks like you will have to run another cable for the modulator output (rather than for the receiver feed, to keep the two existing feeds equal, mainly), or use a wireless transmitter/receiver system to feed the audio/video to the relocated modulator (moved to where its output can feed the rest of the house's coaxes).

Another possibility is, as you mentioned, a CAT-5 distribution method. In any case, I'd save the already-installed coaxes for the receiver. You want the best signal to feed the receiver.

Larry
www.fineelectricco.com

This message was edited by Larry Fine on 03/19/02 02:31.02.
OP | Post 4 made on Tuesday March 19, 2002 at 09:14
jfetter
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On 03/19/02 02:19.00, Larry Fine said...
To explain how a multiswitch works, and why splitting
one (the A) cable won't work...

Thank's for the explanation Larry. Now that I understand (or think I do), I do have a follow up question. If a dual LNB really works like 2 single LNB's, I am still not quite certain why I can't split just the "A" or "B" side in my theater. I do understand I can't split the signal from a multiswitch (already split) but that is not what I am suggesting. I do not yet have the multiswitch hooked up yet, I purchased one (Terk) and am prepared to hook it up as I do need more than 2 feeds now. Should I hook it up at my gateway hub and feed 2 of the multiswitched feeds down to the theater (as you suggest) or feed one of the LNB feeds down to the theater and split it there? Maybe I am missing something and you can't split the signal from a single LNB and it is just a bad assumption.

I swear I read you post but the part about it being treated as two single LNB's (and assuming you can split a single LNB) confuses me. Also, if you answer no to the split, can you verify that using the multiswitch at the gateway hub and feeding 2 of the outputs down to the theater, using a diplexer on one of the multiswitched feeds to feed the modulated channels back up to the multiswitch, where I can then feed that to anyplace I want, will work.

Hopefully you followed that...

Thanks for the reply,

Jack Fetter
Post 5 made on Tuesday March 19, 2002 at 10:21
Larry Fine
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|If a dual LNB really works like 2
single LNB's, I am still not quite certain why
I can't split just the "A" or "B" side in my theater.

That's because each receiver sends the DV to the LNB. Remember, unlike cable TV, DSS cabling carries signals in both directions. Trying to split a dish feed would have two receivers feeding DC to the same LNB, which would probably lead to equipment failure.

Should I hook it up at my gateway hub and feed
2 of the multiswitched feeds down to the theater
(as you suggest) or feed one of the LNB feeds
down to the theater and split it there? Maybe
I am missing something and you can't split the
signal from a single LNB and it is just a bad
assumption.

Sorry, but I don't know what you mean by a 'gateway hub', unless you're referring to a cable modem and ethernet hub. Perhaps you mean a distribution panel?

Again, you can't split a cable between a receiver and dish. The output of a receiver can be split, however, but you will only be able to watch the same channel on both TVs, just as if you split the output of a cable tuner.

I swear I read you post but the part about it
being treated as two single LNB's (and assuming
you can split a single LNB) confuses me. Also,
if you answer no to the split, can you verify
that using the multiswitch at the gateway hub
and feeding 2 of the outputs down to the theater,
using a diplexer on one of the multiswitched feeds
to feed the modulated channels back up to the
multiswitch, where I can then feed that to anyplace
I want, will work.

If you mean trying to feed the same piece of wire from both ends, using a diplexer at each end, I've never heard of it, but it might work. Interesting idea. Anybody???

Larry
www.fineelectricco.com
OP | Post 6 made on Tuesday March 19, 2002 at 10:44
jfetter
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On 03/19/02 10:21.55, Larry Fine said...

That's because each receiver sends the DV to the
LNB. Remember, unlike cable TV, DSS cabling carries
signals in both directions. Trying to split a
dish feed would have two receivers feeding DC
to the same LNB, which would probably lead to
equipment failure.

Got it (I think). So it appears you can't split a single LNB to feed more than one receiver as I originally assumed, correct?

Sorry, but I don't know what you mean by a 'gateway
hub', unless you're referring to a cable modem
and ethernet hub. Perhaps you mean a distribution
panel?

Sorry, Bell Atlantic (now Verizon) calls the distribution panel they use in their pre-wired homes a "residential gateway hub". I of course mean the distribution panel.

Again, you can't split a cable between a receiver
and dish. The output of a receiver can
be split, however, but you will only be able to
watch the same channel on both TVs, just as if
you split the output of a cable tuner.

Yea, got that, that's how I feed the modulated DSS and DVD signals back into the cable, by taking the second output of both devices and feeding them into a 2-channel modulator.

If you mean trying to feed the same piece of wire
from both ends, using a diplexer at each end,
I've never heard of it, but it might work.
interesting idea. Anybody???

That's exactly what I mean. The Terk multiswitch has an input for off-air/CATV that it combines with the satellite signal at the 4 outputs. Having a diplexer at the other end would allow me to extract that off-air/CATV signal. INSTEAD of connecting an off-air/CATV input to the multiswitch, I would like to feed the modulated CATV signal INTO the diplexer (in the theater) back up to the Terk multiswitch (to the off-air/CATV input, though I would be using it as the output) and then feed this signal back into my distibution panel to feed the TV in question.

Make sense? damn I hope so as I am getting a little dizzy reading it over again. Bottom line, does the off-air/CATV input on a multiswitch act only as an input or would it work as an output if a signal was fed into a downstream diplexer?

Thanks again Larry...

Jack Fetter
Post 7 made on Tuesday March 19, 2002 at 16:03
Larry Fine
Loyal Member
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Jack, I get it now! I would suggest you try what you want to do, but with one exception:

Feed the modulator into the VHF/UHF connector on the diplexer at the theater end, but use another diplexer before the multiswitch at the upper end to "filter" the modulator signal out of the coax before it gets to a multiswitch output connector.

I would not feed a signal into an output, as there is circuitry within the multiswitch, besides the diplexing, that is probably not two-way capable, as it's most likely not passive.

Please let us know if this works. I'm sure there ae others who could benefit from your experience. That's why we're here!

Larry
www.fineelectricco.com
OP | Post 8 made on Wednesday March 20, 2002 at 09:25
jfetter
Founding Member
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41
Jack, I get it now! I would suggest you try what
you want to do, but with one exception:

Feed the modulator into the VHF/UHF connector
on the diplexer at the theater end, but use another
diplexer before the multiswitch at the
upper end to "filter" the modulator signal out
of the coax before it gets to a multiswitch
output connector.

I would not feed a signal into an output, as there
is circuitry within the multiswitch, besides the
diplexing, that is probably not two-way capable,
as it's most likely not passive.

I was under the impression that a multiswitch with an off-air/CATV input functioned like a simple diplexer (not the entire multiswitch obviously, just the combining of 2 signals). Can it really be one-way? By Passive vs Active do you mean powered? The Terk is not powered, though I am not sure if that factors into the equation.

I did purchase some extra diplexers as my original idea was to use 2 but then I started thinking, that the input on the multiswitch for off-air/CATV seems to be nothing more than a diplexer input/output. Will harm come if I try and user the multiswitch to seperate the signals? Should I use a DC block filter someplace?

Please let us know if this works. I'm sure there
are others who could benefit from your experience.
That's why we're here!

I absolutely will, I plan on swapping out my SAT-A55 with the SAT-W60 on Friday, I'll let you know how it all worked out. I do plan on trying to feed the modulated signal into a diplexer in the Theater and extract if via the multiswitch first unless someone comes back and says not to. I truely don't see how that input on the multiswitch is anything other than the same thing as a regular diplexer.

Thanks again Larry...

Jack Fetter
Post 9 made on Wednesday March 20, 2002 at 21:59
Larry Fine
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Jack, the multiplexer is "powered", even if it has no external power supply; the receiver's send a DC voltage up the line, remember? It is used by the multiswitch. I have a 3-in/8-out, and it's sending out seven signals, without using a separate supply.

I don't think anything will be damaged by trying your idea. The diplexers internally block DC from the antenna connector.

Larry
www.fineelectricco.com
OP | Post 10 made on Thursday March 28, 2002 at 11:13
jfetter
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Well, as promised, I wanted to update anyone interested in this topic. I hooked everything up as planned last night and to my surprise (though it seems a logical conclusion) it worked perfectly. I used the multiswitch in the wiring hub to "extract" the off-air/CATV signal I feed in from a diplexer in my Theater to be able to route it to the TV upstairs. Apparently, a signal can be diplexed in either direction and the multiswitch off-air/CATV input works just like a diplexer and can be either an input or output, depending on the need. In my case I don't have CATV (high speed internet yes, cable TV, ick!) and wanted to use the multiswitch to extract a modulated video feed from the Theater into the master bedroom. This allows me to watch DVD, Satellite ot view the 400 CD-changer titles from bed (I have an infrared eye in the ceiling that passes signals downstairs to the Theater).

If anyone finds this unclear and is interested in doing something similar, just ask, I can attempt to re-phrase it if necessary...

Thanks again Larry for all your help!

Jack Fetter


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