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Digital SWM theory and speculation


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236 replies to this topic

#181 OFFLINE   peds48

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Posted 14 February 2014 - 08:49 PM



NACE -- "North American Cable Equipment" ;

 

Main webpage here;

 

http://www.northamericancable.com/ 

 

DSWM13 product listing is here;

 

http://www.northamer...ID.php?pid=3680

 

(Product ID: CDSWM13R0-01)

 

Have to log in to see prices.

I logged in to see the price, but it says "Price$ Call for pricing" 

 

NACE.pngClick for large view - Uploaded with Skitch


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#182 OFFLINE   slice1900

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Posted 14 February 2014 - 10:32 PM

Yeah, they have a lot of "call for pricing" on their site, which is annoying, but they had something I was having trouble finding elsewhere so I had to call anyway and asked about the DSWM13's price while I was at it.

 

They even have call for pricing on the SWM8/16/32. I don't know if that's because they change prices often or because they don't want their prices to show up in search engines.


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#183 OFFLINE   bobnielsen

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Posted 14 February 2014 - 11:35 PM

Yeah, they have a lot of "call for pricing" on their site, which is annoying, but they had something I was having trouble finding elsewhere so I had to call anyway and asked about the DSWM13's price while I was at it.

 

They even have call for pricing on the SWM8/16/32. I don't know if that's because they change prices often or because they don't want their prices to show up in search engines.

Hmmpf, they don't even list the SWM5.  Mine must be priceless (and it's still working after all these years). :rotfl:



#184 OFFLINE   peds48

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Posted 15 February 2014 - 02:56 PM

Yeah, they have a lot of "call for pricing" on their site, which is annoying, but they had something I was having trouble finding elsewhere so I had to call anyway and asked about the DSWM13's price while I was at it.

 

They even have call for pricing on the SWM8/16/32. I don't know if that's because they change prices often or because they don't want their prices to show up in search engines.

So what is it?


Here’s to the crazy ones.
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#185 OFFLINE   P Smith

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Posted 15 February 2014 - 03:44 PM

So what is it?

hello ? post#177



#186 OFFLINE   peds48

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Posted 15 February 2014 - 03:47 PM

hello ? post#177

It would of have cost you less words to type $185 instead.  but thanks! 


Here’s to the crazy ones.
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The round pegs in the square holes.

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They’re not fond of rules, and they have no respect for the status quo.


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#187 OFFLINE   P Smith

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Posted 15 February 2014 - 06:01 PM

hope you'll keep reading, not like other ppl who prefer [sometimes with excuses] ask, ask, ask ... w/out check the same thread...



#188 OFFLINE   peds48

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Posted 15 February 2014 - 07:52 PM

hope you'll keep reading, not like other ppl who prefer [sometimes with excuses] ask, ask, ask ... w/out check the same thread...

Right, I have read this entire thread, I just happened to either missed that part or did not remember.  I just went over my head....  Woooosshhh


Here’s to the crazy ones.
The misfits. The rebels.
The the troublemakers.
The round pegs in the square holes.

The ones who see things different.
They’re not fond of rules, and they have no respect for the status quo.


Think Differently 

#189 OFFLINE   slice1900

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Posted 21 February 2014 - 10:59 AM

Responding to a post in another thread here, since I'm delving into utter speculation and don't want to make VOS or Stuart have to go to the trouble of moving posts again :)

 

 

Anyhow, based on VOS' mention of the DSWM hi-lo SWM carrier frequencies here, it ("finally") looks like the answer to the DSWM13 center carrier frequencies are;

 

I have been assuming that learning the channel spacing would tell me whether or not the EN5400 (which we know is used in the DSWM13 per the Entropic press release) is an older version of the DSWM ASIC than the one from the paper. Since the paper describes an ASIC capable of 24 channels, this implies it must use a channel spacing less <= 50 MHz.

 

So if the DSWM13 is now known to use a wider channel spacing, it must be an older version, right? I'm not so sure... I find the choices for the channel/frequency pairs a bit disquieting to blithely make that assumption. The ASIC is basically a DSP, it is programmable. It may be capable of 24 channels, but it is flexible enough that it can be programmed for fewer channels and a wider spacing. The question, why would they do that? Why take something capable of 24 channels and program it to use only the 21 that the EN5400 is capable of?

 

I would have pretty much dismissed that scenario since it doesn't make sense, except for the fact that the frequencies for the EN5400 version of the DSWM ASIC were deliberately chosen to mirror those of the ASWM, except with additional channels inserted between them. i.e. ASWM (guide) channel 1 = DSWM (guide) channel 1, ASWM channel 2 = DSWM channel 3, and so on. If I had to bet, I would have said that SWM probably assigns frequencies, not channel numbers, but the more I think about it, the more I think that mirroring ASWM frequencies points toward SWM assigning by channel number - I can't think of a good reason to do that if it was assigning by frequency.

 

So why mirror the ASWM frequencies? Does that somehow make receivers more compatible? Perhaps the DSWM has a "pretend I'm an ASWM" mode where it responds exactly as an ASWM would and assigns odd numbered channels from 3 to 19 (matching ASWM channels 2 to 9) to receivers that don't give it the secret "I know what a DSWM is" handshake? From a software standpoint, you see this sort of thing all the time. All the protocols on the internet for stuff like sending email or downloading a web page are backward compatible to interoperate with the earliest versions of software. Newer versions of software "introduce" themselves to a server in different ways, which lets that server know how to talk to it and what functionality it should make available. In this way, receivers running outdated firmware could still interoperate with a DSWM in "ASWM fallback mode", and eventually become DSWM compatible once they received a firmware update.

 

Still, this isn't quite a satisfactory answer - why 21 channels? At 51.03 MHz between channel centers, there's room for 23 of them. Maybe because 20 (user) channels is a nice round number and 22 is sort of oddball? I thought knowing the channel spacing would make things more clear, but I think now I'm more confused :scratch:

 

The other way to tell whether the EN5400 is an older version of the ASIC is by power consumption, but unless Stuart or someone else with access to a DSWM13 volunteers to take the time to connect one to a dish and connect its power supply to a Kill-o-Watt meter it might be a while to learn this. Since Sonora has published measured power for the SWM8 and SWM16, I'm hoping they will do so for the DSWM13 at some point. We know it uses the same 29v supply as the SWM8 and SWM16, but that tells us nothing about its actual power draw. Since the 45nm ASIC has a maximum draw of 9.4 watts with all 14 input bands active, I believe a module built around it should consume in the ballpark of 11 or 12 watts when connected to a SL5 (including VRM and power supply losses)


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#190 OFFLINE   veryoldschool

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Posted 21 February 2014 - 04:09 PM

You continue to look at this from the wrong direction and have to find complicated "solutions".

After my other post, "I knew" you were going to go around three sides of "Robinhood's barn" to get to the same place.

 

13 channels [plus guide] are used because of the loop thru application limitations.

The LNB is cloned from the DRE.

 

I gave you a test setup, yet your response doesn't seem to show interest in checking it out.

Is this because it would hinder your speculation?

 

I don't know the FSK command structure, but I would think it uses the simplest and easiest method.

Since the receiver has to make a number of changes for SWiM mode, the majority of the firmware resides in the receiver.

The SWiM [ASWM or DSWM] "reports" what it is to the receiver and the receiver "must know" what to do with it.

 

Channel selection may start at the receiver and be confirmed by the SWiM.

With the ASWM it wasn't known which initiated/controlled this as it was automatic.

DRE has added a choice option which "suggests" the receiver is.


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#191 OFFLINE   veryoldschool

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Posted 21 February 2014 - 05:15 PM

From a software standpoint, you see this sort of thing all the time. All the protocols on the internet for stuff like sending email or downloading a web page are backward compatible to interoperate with the earliest versions of software. Newer versions of software "introduce" themselves to a server in different ways, which lets that server know how to talk to it and what functionality it should make available.

"Apples and Oranges"

The internet is open loop and DirecTV is closed loop.


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#192 ONLINE   HoTat2

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Posted 21 February 2014 - 06:49 PM

 

 

... 13 channels [plus guide] are used because of the loop thru application limitations.

 

And these application limitations to 13(14 with guide) SWM channels are primarily due to ....?

 

Such higher SWM frequencies would suffer greater attenuation rates in loop-thru cabling typologies?  


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#193 OFFLINE   veryoldschool

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Posted 21 February 2014 - 08:07 PM

And these application limitations to 13(14 with guide) SWM channels are primarily due to ....?

 

Such higher SWM frequencies would suffer greater attenuation rates in loop-thru cabling typologies?  

Guess you missed this in the first thread.

The DSWM13 loop thru is for the DRE market, which uses DECA and the node limit combined with the DECA losses are the limiting factor.

The DSWM13 has higher output for the taps, but there [to date] isn't a way to boost DECA.


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#194 OFFLINE   peds48

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Posted 21 February 2014 - 08:30 PM

Guess you missed this in the first thread.

The DSWM13 loop thru is for the DRE market, which uses DECA and the node limit combined with the DECA losses are the limiting factor.

The DSWM13 has higher output for the taps, but there [to date] isn't a way to boost DECA.

Why would that be?  Just curious...


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The round pegs in the square holes.

The ones who see things different.
They’re not fond of rules, and they have no respect for the status quo.


Think Differently 

#195 ONLINE   HoTat2

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Posted 21 February 2014 - 08:37 PM

Nope, I remember;

 

Sorry, just brain-lock. smiley-vault-signs-053.gif


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#196 ONLINE   HoTat2

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Posted 21 February 2014 - 08:42 PM

Why would that be?  Just curious...

Because since a DECA signal is two-way on the same coax line and frequency, a DECA amplifier would have to operate bi-bidirectionally on the same line this way as well.

 

No practical way to do that, or else I imagine would be quite expensive if there was a way.


Edited by HoTat2, 21 February 2014 - 08:46 PM.

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#197 OFFLINE   veryoldschool

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Posted 21 February 2014 - 09:14 PM

Why would that be?  Just curious...

DECA is bidirectional, which would require a "unique" amplifier design. 


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#198 OFFLINE   veryoldschool

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Posted 21 February 2014 - 09:16 PM

Because since a DECA signal is two-way on the same coax line and frequency, a DECA amplifier would have to operate bi-bidirectionally on the same line this way as well.

 

No practical way to do that, or else I imagine would be quite expensive if there was a way.

I have had a design for a while now, but the need/market has yet to be found.


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#199 OFFLINE   slice1900

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Posted 21 February 2014 - 09:19 PM

You continue to look at this from the wrong direction and have to find complicated "solutions".

After my other post, "I knew" you were going to go around three sides of "Robinhood's barn" to get to the same place.

 

13 channels [plus guide] are used because of the loop thru application limitations.

The LNB is cloned from the DRE.

 

I gave you a test setup, yet your response doesn't seem to show interest in checking it out.

Is this because it would hinder your speculation?

 

I don't know the FSK command structure, but I would think it uses the simplest and easiest method.

Since the receiver has to make a number of changes for SWiM mode, the majority of the firmware resides in the receiver.

The SWiM [ASWM or DSWM] "reports" what it is to the receiver and the receiver "must know" what to do with it.

 

Channel selection may start at the receiver and be confirmed by the SWiM.

With the ASWM it wasn't known which initiated/controlled this as it was automatic.

DRE has added a choice option which "suggests" the receiver is.

 

 

I already said I'd try your test when I get a chance. You've only given me half a day since you suggested it and you're already calling me out for not trying it? Sorry, but I can't tear apart my system at a moment's notice. Hopefully I'll get a chance to try it sometime next week. If you think I'm avoiding trying stuff because it would "hinder my speculation" then you really aren't paying attention. I often mention ways to test various ideas, even though some of those tests aren't feasible/likely to try so long as the DSWM is limited to the DRE market. As I've said repeatedly I want to be able to narrow down the range of speculation by either proving or ruling out certain ideas or possibilities.

 

Interesting that the DRE receivers can choose their channel. You've stated that the DECA loss was the ultimate reason for the limit of 13 receivers in a loop rather than the theoretical maximum of 15, but do you think channel fixing figures into this at all? Would the difference in cable/tap loss between 1025 MHz and 1637 MHz be large enough that the ability to fix the channel assignment in receivers would be beneficial, to avoid having the last receiver in the loop 300' away using the highest channel number/frequency?

 

Your suggestion that the receiver is in charge of channel selection is quite interesting when taken together with HoTat2's suggestion that the process may be very similar to that in the Euro CSS standard which Entropic also designed. Based on his brief description of that process, it sounds like the receiver submits a channel number / frequency pair "for approval". If SWM uses a similar scheme, using all the same frequencies the ASWM uses would make it simple for a DSWM to interoperate with receivers that have older firmware that only recognizes the ASWM.

 

As you seem to be implying, when the SWM protocol was designed it probably made a lot of sense to put the receiver in charge of as much as possible, since the receiver has most of the "smarts" and all of the programmability/updateability in the relationship. I'm trying to think if there's a way to confirm the receiver is initiating channel selection. I'll have to read that Euro CSS doc and see if triggers any ideas. If an A/B switch was able to switch things quickly enough that the receivers and SWM didn't "notice", it's possible there may be a way to test this...


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#200 OFFLINE   veryoldschool

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Posted 21 February 2014 - 09:32 PM

Interesting that the DRE receivers can choose their channel. You've stated that the DECA loss was the ultimate reason for the limit of 13 receivers in a loop rather than the theoretical maximum of 15, but do you think channel fixing figures into this at all? Would the difference in cable/tap loss between 1025 MHz and 1637 MHz be large enough that the ability to fix the channel assignment in receivers would be beneficial, to avoid having the last receiver in the loop 300' away using the highest channel number/frequency?

Adding the option/flexibility shows DirecTV feels it's beneficial, or they wouldn't have done it.


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