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DSWM13 Switch


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373 replies to this topic

#226 OFFLINE   inkahauts

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Posted 10 December 2013 - 03:35 PM

I'm not sure what you mean by "this works with coax networking [DECA] and that is the limiting factor"? Can you explain further?

It looks like the primary difference between this and previous SWMs, other than five more tuners on a SWM output, is that the legacy outputs are stronger, similar to a SWM32, and based on the drawing, supported to cascade at least three levels deep. The SWM output maybe be stronger as well, assuming the "300 feet" thing means 300 feet to the 13th tap.

I wonder what the design target is for the output level at each tap? I guess receivers would need an output of -55 dbm, as IIRC that's what Directv considers the minimum output level they're guaranteed to work at. I think DECA may need more, but since it is lower frequency and experiences less loss through coax and taps designing based on receiver losses should keep DECA within margin.

What I don't understand is why using taps in this manner wouldn't work just as well on a SWM8. Am I missing something? Looking at the entire drawing, everything I see there could be addressed with current equipment as far as I can tell, by adding an amp and four way splitter off each trunk tap since SWM8s can't cascade (or using a single SWM32) and adding SWM amps to compensate for the assumed difference in SWM output strength. The only capability there is no substitute for is having 13 tuners from the SWM output instead of 8, which I imagine is probably the key to making this solution work for this market, otherwise it would have been marketed using SWM8s years ago, since the only missing piece is designing a SWM tap.

Is the difference between 8 and 13 sort of a "magic number" in terms of how hotels are typically wired? That is, is there a best practice that has typically been followed for doing the loop through wiring in hotels that says to not exceed 10 or 12 rooms on a single loop? Obviously if you have a hotel with >8 rooms in a loop a SWM8 is useless, but if you have >13 rooms in a loop the DSWM13 would be as well, so I'm assuming that typically hotels aren't wired with more than 13 rooms per loop?


He's maybe talking about the fact that deca has a node limit/ distance?


And for the reason 13 is so much more important than 8, look at the doc again. There is specific mention about the networking switch and how many it needs versus an older system... We are talking about a lot of money there too. The dre is evidently very much network driven...

Edit.. Vos beat me to it!

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#227 OFFLINE   veryoldschool

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Posted 10 December 2013 - 04:18 PM

What I don't understand is why using taps in this manner wouldn't work just as well on a SWM8. Am I missing something? Looking at the entire drawing, everything I see there could be addressed with current equipment as far as I can tell, by adding an amp, since the only missing piece is designing a SWM tap.

I could make this work, "but" I'd need to have a lot more equipment closets.


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#228 OFFLINE   Diana C

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Posted 10 December 2013 - 04:55 PM

But what I'm saying is, is there any reason I couldn't obtain some of the taps they're using, and use them on a current SWM? There's nothing magical about a SWM8's output that it can only work with splitters, and not taps. The reason they use taps is because they have much less loss than splitters - the DSWM13 would require much higher output levels than what it has now if it had to drive 12 splitters in series instead of 12 taps in series.

 

The problem is that the signal output of a standard SWM is way too low to start with.  The taps don't have less loss, they just allocate it differently. A two way splitter outputs 50% of the incoming signal strength to each side of the split.  Let's say for the sake of argument that a tap passes 90% down the trunk and 10% to the "tapped" line.  To get a signal that is usable to a receiver from a standard SWM would require more amplification than any amplifier can produce.  Even if you were able to disable the gain control on a amp such that it did output a hot enough signal, you now run the risk of someone slapping a standard splitter infront of a receiver, or worse, connecting a receiver to the "trunk."  Stand back if that happens...you might see the receiver fly across the room in a trail of smoke and embed itself in the wall. :)

 

I doubt you'll ever see this approach used in homes...it just is too risky to be used in an environment were the homeowner is likely to make changes to the wiring.


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#229 OFFLINE   Stuart Sweet

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Posted 10 December 2013 - 04:57 PM

That's an excellent point, Diana. You are a very smart person.
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#230 OFFLINE   Diana C

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Posted 10 December 2013 - 05:05 PM

I'm just reading what the white paper says...well written piece, IMHO. :)


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#231 OFFLINE   veryoldschool

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Posted 10 December 2013 - 05:09 PM

The problem is...

I think you exaggerated to make your point.

A SWM8 outputs -30 dBm, which can be boosted to -20 dBm, which "Oh by the way" is the max input spec for the receiver.

 

Tap Value 6dB 9dB 12dB 16dB 20dB
MoCA        4      3      2       1.5   1.3 
950MHz    4.5   3.5   2.5     2.1   1.9
2150MHz   4.8  3.8   2.8     2.5   2.3


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#232 OFFLINE   Diana C

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Posted 10 December 2013 - 05:15 PM

I think you exaggerated to make your point....

Indeed, and I hope it was at least a little humorous as well.  I just have this mental image of a receiver partially embeded in a wall, with sparks and smoke coming from it. :)  I know it wouldn't really happen that way.  More likely, you'd just turn the receiver into a door stop with no visible effects at all - but where's the fun in that?


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#233 OFFLINE   veryoldschool

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Posted 10 December 2013 - 05:23 PM

Indeed, and I hope it was at least a little humorous as well.  I just have this mental image of a receiver partially embeded in a wall, with sparks and smoke coming from it. :)  I know it wouldn't really happen that way.  More likely, you'd just turn the receiver into a door stop with no visible effects at all - but where's the fun in that?

I sometimes need a 2x4 to get the point across. It's not as humorous, but hopefully lasts awhile.

 

The DSWM13 will "never" be a DIY install, and "I'd bet" there will be a few AIMs [meters] that will go "poof" before too long too, since they require a 10 dB pad to be used.

"Smoke'em if you gotten'em" !rolling


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#234 OFFLINE   slice1900

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Posted 10 December 2013 - 05:23 PM

He's maybe talking about the fact that deca has a node limit/ distance? And for the reason 13 is so much more important than 8, look at the doc again. There is specific mention about the networking switch and how many it needs versus an older system... We are talking about a lot of money there too. The dre is evidently very much network driven... Edit.. Vos beat me to it!

 

Nework switches are so cheap, reducing the number of them can't possibly be a motivation. Assuming more expensive managed switches are required to allow the 'master control system' to monitor them, 16 port managed switches from reputable vendors like Cisco and HP cost a couple hundred dollars, you can add additional switches as necessary.

 

The difference between 13 rooms per switch port and 8 rooms per switch port amounts to a buck or two a room.


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#235 OFFLINE   veryoldschool

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Posted 10 December 2013 - 05:25 PM

Nework switches are so cheap, reducing the number of them can't possibly be a motivation. Assuming more expensive managed switches are required to allow the 'master control system' to monitor them, 16 port managed switches from reputable vendors like Cisco and HP cost a couple hundred dollars, you can add additional switches as necessary.

 

The difference between 13 rooms per switch port and 8 rooms per switch port amounts to a buck or two a room.

You're on the wrong track.

It has to do with the MoCA.


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#236 OFFLINE   Stuart Sweet

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Posted 10 December 2013 - 05:38 PM

Sorry Slice1900, you're way off here. This system won't work with that $50 switch you buy at Staples and you can't just add more switches, either willy or nilly. This is a very specific installation that's being built here, it's not a whitebox special. Everything about it is proprietary and unique.

Golly jeepers I wish I could be more precise and explain more at this point, I just can't. I will say that your "buck or two a room" estimate is missing a few zeroes. If you'll stipulate to the fact that you can't use SWM8s for loop-through, just trust me on that, the cost to rewire a hotel for home run can get into the six figures on some convention hotels. So using DSWMs with loop through ends up being a ton cheaper even if the multiswitches themselves are more expensive.
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#237 OFFLINE   slice1900

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Posted 10 December 2013 - 05:39 PM

You're on the wrong track.

It has to do with the MoCA.

 

OK, you're talking about needing one DECA per 13 rooms rather than one DECA per 8. At list pricing that is a pretty significant savings!


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#238 OFFLINE   Diana C

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Posted 10 December 2013 - 05:44 PM

Nework switches are so cheap, reducing the number of them can't possibly be a motivation. Assuming more expensive managed switches are required to allow the 'master control system' to monitor them, 16 port managed switches from reputable vendors like Cisco and HP cost a couple hundred dollars, you can add additional switches as necessary.

The difference between 13 rooms per switch port and 8 rooms per switch port amounts to a buck or two a room.

I would think it is more like the difference between a port for EVERY room (actually receiver...I'm in a hotel room right now with two HD TVs) and one port per 13 rooms/receivers. In a medium size hotel (300 rooms) that's the difference between 300 ports and 23 ports, or 17 fewer switches. But the real savings is in not needing a Cat 5 run into every room...now you are talking about many thousands of dollars in savings.

Remember...we are putting receivers or DVRs into each room. The guest can make a certain amount of customization of the unit (favorites list, sort order, etc.). The hotel wants to be able to wipe that out without going to every single room (you don't want to try and teach housekeeping to do it). So a network connection is needed for management of the receiver. By using MOCA, the A/V and the management is supported by a single cable (and one that is already in place).

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#239 OFFLINE   veryoldschool

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Posted 10 December 2013 - 05:47 PM

OK, you're talking about needing one DECA per 13 rooms rather than one DECA per 8. At list pricing that is a pretty significant savings!

"There's that too"

I think more important though is the amount of "real estate" required for the hardware, and it "would have been" a DSWM15 if the MoCA loss wasn't a problem. 


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#240 OFFLINE   Diana C

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Posted 10 December 2013 - 05:53 PM

"There's that too"
I think more important though is the amount of "real estate" required for the hardware, and it "would have been" a DSWM15 if the MoCA loss wasn't a problem.


Excellent point...you don't want to have to dedicate a guest room to hold all the racks of switches (LAN and satellite).

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#241 OFFLINE   AntAltMike

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Posted 10 December 2013 - 06:04 PM

As far as I know, all the current manufacture "taps" I use in multiple dwelling units are DC blocked and the low frequency ratings are commonly 47 MHz, so they may not be suitable for carrying a 2.3 MHz upstream signal. Back in the early 2000s, some manufacturers started labeling their taps as 5 MHz taps, but this industry is notorious for passive product ratings that do not have much integrity. I remember that back when I used to diplex cable TV internet signals with satellite signals in condominiums, I got better performance, which is to say, less loss, on 10 Hz return signals going through Sonora passive products that were rated down to 15 MHz than with other inexpensive products whose labels said they were good to 5 MHz. Those of us who were doing commercial satellite L-band distribution work in the late 1990s may remember that there were lots of splitters bearing labels that said 2,150 MHz where you could peel off that label and the one underneath it said 1,450 MHz. When I fed DirecTV's stacked 2,025 signals through them, they rolled off typically seven or eight dB over that last, or highest 500 MHz.

So if an existing tap label says it is rated to 5 MHz, that wouldn't necessarily make it a brick wall to 2.3 MHz return signals, but it would still pose a practical problem for DirecTV, because they would have no way of ascertaining just how much those dubiously rated 5 MHz taps really rejected 2.3 MHz. My guess for the "how do they do this" sweepstakes is that the return frequency will be higher than 2.3 MHz, and that they utilize the cable TV band to the extent that they may not even have to go to, IIRC, 1890 MHz to stuff 13 dedicated transponders into their plan. Depending on that they can "get away with" for guard bands, they may not even have to go to the L-band.

Edited by AntAltMike, 10 December 2013 - 06:15 PM.


#242 OFFLINE   veryoldschool

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Posted 10 December 2013 - 06:11 PM

As far as I know,

this industry is notorious for passive product ratings that do not have much integrity.

There will be two different part numbers for the taps "before" and "after" the DSWM13, so "SWiM" taps will pass the 2.3 FSK


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#243 OFFLINE   Stuart Sweet

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Posted 10 December 2013 - 06:13 PM

No existing taps may be used for this system as specified. There are no currently manufactured taps that are approved for this purpose, and the new ones... the ones that are... are still secret.
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#244 OFFLINE   slice1900

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Posted 10 December 2013 - 06:37 PM

Sorry Slice1900, you're way off here. This system won't work with that $50 switch you buy at Staples and you can't just add more switches, either willy or nilly. This is a very specific installation that's being built here, it's not a whitebox special. Everything about it is proprietary and unique.

Golly jeepers I wish I could be more precise and explain more at this point, I just can't.

 

I don't want you to think I'm asking or expecting you to release details you're not allowed to at this time. I've been subject to NDAs or "understandings" about stuff like this many times before.

 

What you're saying is that everything is sold to customers as a complete package. The fact that pretty much any switch will work (and I can assure you that's the case, ethernet is ethernet) is immaterial because you get what Directv provides you with, and if it breaks you call them for service and it is replaced with the same model or whatever updated model they're using at the time. They may sell a switch 5x more than what it costs if you bought the identical model elsewhere, but you're paying for the support of the product as a whole, not buying parts piecemeal. That's referred to in the IT world as a turnkey system.

 

I think we're sort of talking around each other here a bit, because I like to talk about technical/theoretical limitations, and you're talking about the product that Directv is selling as a complete package. Whether changing something in even the tiniest way still works or not is irrelevant to you, because there is only one way this system can be sold and supported.

 

At any rate, we're straying pretty far from the DSWM13 itself that's the subject of this thread, so I'll shut up for now and when you can release more info next year I'll understand the things I'm missing a bit better :)


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#245 OFFLINE   Stuart Sweet

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Posted 10 December 2013 - 06:40 PM

Yeah I'm glad you understand. Of course, yes, I am talking about a turnkey system because for the foreseeable future that is the one and only way this product will be available. I know it seems like we're talking about two different things but since this product will only be part of a turnkey system, I tend to think of the whole system.

I can tell you this, since it applies to current technologies, the process for getting approved for DRE is very comprehensive and DRE system bills of materials are subject to DIRECTV approval. No substitutions allowed. The good news is the hardware really isn't more expensive than comparably configured units; you just pay for the staging and site work.
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#246 OFFLINE   slice1900

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Posted 10 December 2013 - 06:58 PM

"There's that too"

I think more important though is the amount of "real estate" required for the hardware, and it "would have been" a DSWM15 if the MoCA loss wasn't a problem. 

 

Interesting.

 

I think I might be circling in on what you're saying. The worst case SWM loss is for the receiver that's furthest from the DSWM13, while the worst case MoCA loss will be to/from the receiver that's closest to the DSWM13, since the DECA adapter is shown at the endpoint of the coax.

 

I'm sure there's a good reason why the DECA adapter is at the far end rather than next to the DSWM13, and that reason probably has something to do with differences in losses when going in/out a tap port.


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#247 OFFLINE   veryoldschool

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Posted 10 December 2013 - 06:59 PM

These are still going to be "big ticket" installs and we won't be seeing "free professional" installation on the work order. :lol:


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#248 OFFLINE   veryoldschool

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Posted 10 December 2013 - 07:02 PM

Interesting.

 

I think I might be circling in on what you're saying. The worst case SWM loss is for the receiver that's furthest from the DSWM13, while the worst case MoCA loss will be to/from the receiver that's closest to the DSWM13, since the DECA adapter is shown at the endpoint of the coax.

 

I'm sure there's a good reason why the DECA adapter is at the far end rather than next to the DSWM13, and that reason probably has something to do with differences in losses when going in/out a tap port.

Huh?

The farthest receiver is still the highest loss be it SWiM or DECA.


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#249 OFFLINE   slice1900

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Posted 10 December 2013 - 07:22 PM

Huh?

The farthest receiver is still the highest loss be it SWiM or DECA.

 

The DSWM13 is at one end of the coax, the DECA adapter is at the other end. If you number the receivers 1 - 13 with one being the closest to the DSWM13 and 13 being the furthest, then receiver 13 has the most SWM loss, but receiver 1 has the most DECA loss.


Edited by slice1900, 10 December 2013 - 07:22 PM.

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#250 OFFLINE   veryoldschool

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Posted 10 December 2013 - 07:28 PM

The DSWM13 is at one end of the coax, the DECA adapter is at the other end. If you number the receivers 1 - 13 with one being the closest to the DSWM13 and 13 being the furthest, then receiver 13 has the most SWM loss, but receiver 1 has the most DECA loss.

You've got it wrong.

The DECA is with the DSWM13.

If it was at the other end, the directional couplers wouldn't work.


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