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Help installing broadband DECA


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33 replies to this topic

#21 OFFLINE   veryoldschool

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Posted 02 April 2011 - 05:03 PM

I don't have the LNB or SWM specs, but possibly the gain of these is high enough that the noise figure is essentially established prior to the splitter with some degree of margin, so that rainfade might not be affected by a small increase in post-SWM loss.

While the NF is fairly well "nailed" in the LNB, you still have losses to the receiver and the more you have/use the sooner the receiver reaches minimum detectable signal levels.
If you work through the losses of a non SWiM system and a SWiM, you'll find the SWiM needs the gain it has to give the same dynamic range and still run through splitters.
A.K.A VOS

#22 OFFLINE   harsh

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Posted 02 April 2011 - 05:53 PM

It isn't a good idea to use a larger splitter than you need, as it just drops the SAT levels more and could cause rainfade sooner.

Splitters on the IF side, regardless of configuration, do not impact the satellite signal strength.

Splitters cut into the IF signal coming from the LNB and the DECA signal traveling to and fro.

Too often we enjoy the comfort of opinion without the discomfort of thought. -- JFK


#23 OFFLINE   veryoldschool

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Posted 02 April 2011 - 06:45 PM

This is so dumb, someone had to PM me about this.

It isn't a good idea to use a larger splitter than you need, as it just drops the SAT levels more and could cause rainfade sooner.

Splitters on the IF side, regardless of configuration, do not impact the satellite signal strength.

Splitters cut into the IF signal coming from the LNB and the DECA signal traveling to and fro.

ANY receiver is going to be affected by the loss feeding it. I doesn't matter if it's the LNB output, or the IF out of the SWiM.
Loss is loss,Redacted.
The only difference at all is the frequency since this affects the amount.
An 8-way splitter adds another 15.5 dB of loss to the coax, so the SWiMs try to compensate for this by having 15 dB of gain when the SAT levels drop below -45 dBm.

Redacted

Edited by Doug Brott, 03 April 2011 - 11:20 AM.

A.K.A VOS

#24 OFFLINE   hdtvfan0001

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Posted 02 April 2011 - 08:32 PM

This is so dumb, someone had to PM me about this.

ANY receiver is going to be affected by the loss feeding it. I doesn't matter if it's the LNB output, or the IF out of the SWiM.
Loss is loss, Redacted.
The only difference at all is the frequency since this affects the amount.
An 8-way splitter adds another 15.5 dB of loss to the coax, so the SWiMs try to compensate for this by having 15 dB of gain when the SAT levels drop below -45 dBm.

Redacted

I feel your pain VOS.

What the heck is a Dish subscriber who has likely never set eyes on a DirecTV WHDS/SWiM setup himself, let alone the actual SWiM hardware (in person), let alone operated at all with it as a DirecTV customer...doing giving ANY advice on this topic?

Redacted.

Over-the-top-utterly ridiculous.

OP - please listen to VOS...he is an expert on this stuff.

Edited by Doug Brott, 03 April 2011 - 11:21 AM.

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#25 OFFLINE   veryoldschool

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Posted 02 April 2011 - 09:02 PM

Loss 101:
The dish outputs x dBm

With setup "A":
The receiver is 200 feet away, so the coax loss can be -18.6 dB @ 2 GHz.

With setup "B":
The receiver is 50 feet away, so the coax loss can be -4.6 dB @ 2 GHz.

Which receiver will lose signal first/longer when the rain gets heavy?

Redacted

Edited by Doug Brott, 03 April 2011 - 11:21 AM.

A.K.A VOS

#26 OFFLINE   K4SMX

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Posted 02 April 2011 - 10:00 PM

Ideally you should have a band stop filter between the SWM and the splitter, to avoid issues from the high level DECA signal. I don't have a filter installed on mine and it works fine, but YMMV.

Actually I have a filter and another splitter but have never gotten around to installing them in the crawl space (at 72, I'm getting to be too old to be crawling around down there unless I really need to).


Many thanks, Bob, and good to hear from you! Understand about the crawl spaces; I don't even like to get on my knees on the floor anymore. Painful!

Another question I have involves the router connection to the splitter through the DECA. The Solid Signal diagram on their web page shows this being connected to the power passing port of the splitter. Currently, of course, that port is occupied by the coax coming from the SWM power inserter on one of the IRD lines. Does it really make any difference which port is used from the router/DECA?

Also, it wouldn't be any trouble to put a Band Stop filter ahead of the SWM3 upstream of the splitter, but can that be done with the SWM power inserter remaining downstream of the splitter on the IRD line? (The SS diagram shows: splitter ---> BSF ---> SWM PI ---> SWM ---> 5LNB Dish)

Thanks again! I've lost track of all this stuff while building towers and antennas at the NC location.
Stew in Florida

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#27 OFFLINE   veryoldschool

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Posted 02 April 2011 - 10:39 PM

Many thanks, Bob, and good to hear from you! Understand about the crawl spaces; I don't even like to get on my knees on the floor anymore. Painful!

Another question I have involves the router connection to the splitter through the DECA. The Solid Signal diagram on their web page shows this being connected to the power passing port of the splitter. Currently, of course, that port is occupied by the coax coming from the SWM power inserter on one of the IRD lines. Does it really make any difference which port is used from the router/DECA?

Also, it wouldn't be any trouble to put a Band Stop filter ahead of the SWM3 upstream of the splitter, but can that be done with the SWM power inserter remaining downstream of the splitter on the IRD line? (The SS diagram shows: splitter ---> BSF ---> SWM PI ---> SWM ---> 5LNB Dish)

Thanks again! I've lost track of all this stuff while building towers and antennas at the NC location.

I'm not bob [duh] but:
The BB DECA [or any other DECA] doesn't care if the port is power passing or not, since the DECA isn't outputting and DC.
The filter does pass DC, so it too can be inline with the SWiM PI and the SWiM.
A.K.A VOS

#28 OFFLINE   K4SMX

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Posted 02 April 2011 - 10:56 PM

.....The filter does pass DC, so it too can be inline with the SWiM PI and the SWiM.


And that's what I needed confirmed, thanks, VOS, and a pleasure once again. So I can go: IRD ---> SWM PI ---> Splitter ---> BSF (or not, per Bob, "YMMV") ---> SWM3

It is somewhat confusing that they put this particular diagram on their web page, with the SWM PI upstream of the splitter and the router/DECA using the PP port of the splitter.
Stew in Florida

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#29 OFFLINE   harsh

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Posted 03 April 2011 - 01:40 AM

I stand by my statement that SWiM splitters have no impact on the satellite signal readings and moreover that they cannot create a situation that manifests as rain fade. What you suggested is false and misleading.

The satellite signal (as reported in Satellite setup menu option) is uniquely a measure of the satellite downlink signal quality received at the LNB feed horn. It does not evaluate the IF signal from the amplifier to the receiver. This is true of pretty much all consumer satellite setups (including broadband and SARS).

The satellite downlink signal travels no farther than the LNB. Within the LNB, the signals are block converted down to the IF and retransmitted by the amplifier section. Adding or subtracting loads on the output of the IF amplifier doesn't impact the quality of the signal the dish reflects into the feed horn one iota.

If you placed a variable attenuator in the line ahead of a receiver, the satellite signal readings would remain constant until that receiver could no longer "see" IF signal. Even then, the satellite signal levels would remain more or less unchanged on any other receivers.

If you don't know or believe what I'm saying to be true, test it. I'm guessing you have access to or can assemble an unbalanced attenuator pad.


As an aside, I would suggest that when you speak of gain or loss, you use percentages instead of dB as those not intimate with the concept of decibels have trouble relating it to anything meaningful. I would suggest using percentage gain or loss.

Too often we enjoy the comfort of opinion without the discomfort of thought. -- JFK


#30 OFFLINE   veryoldschool

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Posted 03 April 2011 - 09:10 AM

Again someone had to PM me about this, as I've told you several times your being ignored.

I stand by my statement that SWiM splitters have no impact on the satellite signal readings and moreover that they cannot create a situation that manifests as rain fade. What you suggested is false and misleading.

I'm not misleading or suggesting false information. You on the other hand don't seem to grasp the concept.

The satellite signal (as reported in Satellite setup menu option) is uniquely a measure of the satellite downlink signal quality received at the LNB feed horn.

what this is [quality] is the carrier to noise ratio, which as long as the signal is ~10 dB above the noise floor, does stay constant.

It does not evaluate the IF signal from the amplifier to the receiver. This is true of pretty much all consumer satellite setups (including broadband and SARS).

Well if you actually had DirecTV AND SWiM, you'd then know that the setup menu does have a screen to measure the IF. It's labeled "SWM" and shows the nine IFs.

The satellite downlink signal travels no farther than the LNB. Within the LNB, the signals are block converted down to the IF and retransmitted by the amplifier section. Adding or subtracting loads on the output of the IF amplifier doesn't impact the quality of the signal the dish reflects into the feed horn one iota.

Cable & splitter losses have nothing to do with the SAT feed to the LNB, and if this was where the receiver was, then the losses wouldn't be there. Since the receiver is what receiver the signal, losses to the LNB plus the losses to the receiver all add together. If these didn't, then Sonora would have the business they do and coax lengths and amps wouldn't matter. If "the load" on the LNB's IF doesn't "impact" the quality of the signal, then coax runs could be hundreds of feet and the receivers would still work fine.

If you placed a variable attenuator in the line ahead of a receiver, the satellite signal readings would remain constant until that receiver could no longer "see" IF signal. Even then, the satellite signal levels would remain more or less unchanged on any other receivers.
If you don't know or believe what I'm saying to be true, test it. I'm guessing you have access to or can assemble an unbalanced attenuator pad.

Since I do have DirecTV, SWiM, and know what I'm talking about, I have run some tests like this to see how low the signal can be before the receiver starts showing "the quality" degrading. I found this to be at about -71 dBm, which was where the highest IF showed a drop of 5% and I ran out of attenuation to go farther. The receiver chip is spec'd to -70 dBm.

As an aside, I would suggest that when you speak of gain or loss, you use percentages instead of dB as those not intimate with the concept of decibels have trouble relating it to anything meaningful. I would suggest using percentage gain or loss.

Percentages work well for bit error rates, but don't for losses, which is why decibels are used.
3 dB is easy @ 50%
6 dB is easy @ 25%
9 dB is easy @ 12.5%
10 dB is easy too @ 10%
20 dB isn't so much @ 1%
30 dB is sort of pointless @ 0.1%
Since we're dealing with dynamic ranges of 50 dB, percentages are basically meaningless.

Now to bring this whole thing back to my post that you replied to:

Using a larger splitter than one needs, will add more loss to the receiver. Since the whole signal path losses all add up, when the SAT signal drops to the LNB, the output of the LNB drops and the losses between the LNB and the receiver causes the receiver's signal to also drop. Reducing the cable/splitter losses, means the receiver will still be above it's minimum detectable signal levels longer.
Using a 4-way splitter instead of an 8-way splitter is much like having 50' less coax between the dish and the receiver.
A.K.A VOS

#31 OFFLINE   veryoldschool

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Posted 03 April 2011 - 11:41 AM

To try to have all of this make some sense to those that don't have an RF background:

http://www.dbstalk.c...=1&d=1301851584

The green is the part of the signal the receiver uses.
The blue is the part that the receiver doesn't show in the setup screens.
The more blue [power] you have the more resistance to rainfade you have.
You can't do anything about the weather, so all you can do is to align the dish as well as you can and keep the loss from the dish to the receiver as low as you can.

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A.K.A VOS

#32 OFFLINE   hdtvfan0001

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Posted 03 April 2011 - 05:49 PM

Thanks VOS.

You have forgotten more on this topic than most folks will ever know on the subject.

It's a shame that legitimate questions and your legitimate responses have to be diluted by misinformation and uniformed posts from non-DirecTV customers, especially those who actually have field experience with SWiM, green splitters, and the like.

Your great data is appreciated.
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#33 OFFLINE   vanzant

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Posted 07 April 2011 - 12:19 PM

This just occured to me. Do I need 2 BB DECA units? One for each receiver???

I only purchased one and was thinking that it would enable VOD on all receivers on the home network. Is that a correct assumption? Or do I need 1 DECA per receiver?

#34 OFFLINE   veryoldschool

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Posted 07 April 2011 - 12:40 PM

This just occured to me. Do I need 2 BB DECA units? One for each receiver???

I only purchased one and was thinking that it would enable VOD on all receivers on the home network. Is that a correct assumption? Or do I need 1 DECA per receiver?

Going off your diagram, where you have "24s", the only other DECA you need is the BB DECA, since the 24s have one internally.
A.K.A VOS




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