# 2 SWM16 with SWM-E2



## ewing453 (Oct 22, 2008)

The directv installer told me his technical trainer said that two swm16 would burn out the E2 after a few weeks. I checked all the specs and the built in power supply has more than enough amperage. He said it would only work with swm8's.

It is working great now, I just need to add the diplexers to bridge the deca cloud. I have 18 tuners right now after the recent genie addition. The installer told me he would have to mount a second dish!! I convinced him to just leave the second swm and I would hook it up.

Anyone else using this configuration?


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## veryoldschool (Dec 10, 2006)

ewing453 said:


> View attachment 30702
> 
> 
> The directv installer told me his technical trainer said that two swm16 would burn out the E2 after a few weeks. I checked all the specs and the built in power supply has more than enough amperage. He said it would only work with swm8's.
> ...


It wouldn't be the E2 that concerns me, but the two SWiM-16s as they're not going to get enough air across them to keep cool.

This is how it's done now:










http://www.solidsignal.com/pview.as...-directv-swm-expand-(swm-e2)&sku=609465599052


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## Tisby (Jun 4, 2010)

I know you're not done connecting things as you said you still need diplexers, but I see several uncapped ports in that picture.


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## hidefman (Dec 16, 2006)

I have the E-2 pictured in OP... used it with two SWM8s... worked great. Then updated to one SWM16. I have now added the HR34 to my SWM16, using all 16 tuners with all my receivers. I have another SWM16 in reserve (bought it at great price, $32). Now I want to change out my H21 and put in HR21, need one more tuner. Been wanting to try the E-2 with two SWM16s vs. parallel setup. I could let the H21 just pull a recording tuner from the Genie, but then I wouldn't have this challenge would I....lol.

VOS, I have compared heat for the SMW8 & the SWM16 and frankly, don't see much difference. So not so sure heat would be the failure point, but could be wrong on that.

Have always wondered if enough amperage would flow to two SWM16s from the E-2's one 24 volt power source, or should I use two power supplys even with E-2. Either way, still have analyze the bridge for two SMWs even with HR34. And yes, I will use the BSF on the Genie because I still ethernet WH.


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## Stuart Sweet (Jun 19, 2006)

I'd skip the SWME2 in this case and use Skywalker dual power passing splitters instead. There's no doubt that the SWME2 would work for the short run, I'm sure of it.

I've observed what seems to be a higher level of radiant heat from a SWM16 than SWM8 but this is simply an observation without detailed measurements.

Since you have the E2 already in place, I'd leave it and see if it gave you problems, and possibly pick up a few of those Skywalker splitters, they aren't too expensive to have around.


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## veryoldschool (Dec 10, 2006)

hidefman said:


> VOS, I have compared heat for the SMW8 & the SWM16 and frankly, don't see much difference. So not so sure heat would be the failure point, but could be wrong on that.


You might take your spare -16 and stack in on top of your working -16. Then see how warm the working -16 gets.
A working -16 can get almost too warm/hot to touch, where my SWM8 would barely feel warm to the touch.


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## doctor j (Jun 14, 2006)

When i wory about HOT components, i put a case fan in to keep it all COOL.

Doctor j


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## veryoldschool (Dec 10, 2006)

doctor j said:


> When i wory about HOT components, i put a case fan in to keep it all COOL.
> 
> Doctor j


You can use "active" cooling, or passive cooling, but cooling is a concern with the -16 more than with the SWM8.


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## hidefman (Dec 16, 2006)

veryoldschool said:


> You can use "active" cooling, or passive cooling, but cooling is a concern with the -16 more than with the SWM8.


okay, VOS and Stuart have convinced me not to use the E-2 Expander with my two SWM16's.... darn it... looked like a pretty clean set-up with just one power inserter.

I'll go with the parallel set-up and two power inserters.


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## veryoldschool (Dec 10, 2006)

hidefman said:


> okay, VOS and Stuart have convinced me not to use the E-2 Expander with my two SWM16's.... darn it... looked like a pretty clean set-up with just one power inserter.
> 
> I'll go with the parallel set-up and two power inserters.


I posted the newer expander which doesn't stack the SWiM-16s, which could let you do what you wanted.


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## hidefman (Dec 16, 2006)

veryoldschool said:


> I posted the newer expander which doesn't stack the SWiM-16s, which could let you do what you wanted.


Yes you did. $69.99. It's just $$...lol


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## veryoldschool (Dec 10, 2006)

hidefman said:


> Yes you did. $69.99. It's just $$...lol


Four Skywalker 2-ways are cheap.


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## hidefman (Dec 16, 2006)

veryoldschool said:


> Four Skywalker 2-ways are cheap.


The fact that I already have two SWM16's complete with two power inserters and (4) 2-way splitters already... I'll just go with the parallel set-up...

...now on to integrating the HR34 into my ethernet only WH or transitioning over to DECA ... along with one or two diplexes along the way because of just one coax...

don't worry VOS, I've been reading your other threads... see you over there, I'm sure.... isn't this fun!


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## SomeRandomIdiot (Jan 7, 2009)

I picked up a SWM32 for a little over $150 and the 24v power inserter for $25. Have a Sonora unit that will power the lnbs so no need for the 18v power inserter. Figure I can sell off my 2 SWM-16s with power supplies to recoup most of that. Simply need a few splitters to make the units work with DECA. Seemed cleaner than dealing with a bunch more splitters and 2 SWM-16s w/ power supplies.


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## hidefman (Dec 16, 2006)

From what understand, a swm32 is way different from two swm16s. You'll have to treat as four separate 8 port banks in every phase of setup.

You need a new different thread than This one


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## Jodean (Jul 17, 2010)

I was just sent this for an mdu project. First board of four in this building.

I see no heat issues that would arise from an E2, the swm 16's are over an inch apart, dont see how that would effect cooling, esp when they are indoors at 70 degress constant.


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## veryoldschool (Dec 10, 2006)

Jodean said:


> I see no heat issues that would arise from an E2, the swm 16's are over an inch apart, dont see how that would effect cooling, esp when they are indoors at 70 degress constant.


All I'll say is "good luck".


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## hidefman (Dec 16, 2006)

Aside from the heat issues, are we sure there should be no problems with adequate voltage, amperage for using the E-2 Expander with (2) SWM16s, or even (1) SWM8 + (1) SWM16?

If I were to configure a SWM8 and SWM16 together with the E-2 Expander pictured above, would messages like 775 and 771A (communications with the dish) indicate power inserter voltage issues? Just wondering if SWM8 + SWM16 might have different requirements from 2 SWM8s connected to the E-2. Keep in mind the single power supply for the Expander is one 24-volt brick.

It took about 24 hours for the problem to present itself. I double checked all the connections and ground. If this is the issue, could one use the Expander as a just splitter for the SWMs? and then use separate power supplies for each SMW? I would think either configuration would work.

More importantly, if the SWMs cannot get adequate power, then Expander configuration is not going to work.

Again, heat issues may well be another major issue. I would say to VOS and to Stuart, I concur with added heat generated by the SWM16. I have stacked the SWM8 and the SWM16 and the heat comparison is very obvious. SWM16 is much hotter. Not sure if the 1" spacing between the stacked SWMs is enough...

The 775 messages and the 771A messages are coming from one receiver on the SWM16/DECA side of the set-up, not the SWM8 side. If I have other issues, I will start another thread for sure...

_*(VOS, the reason I am using a SWM8: My plan is a hybrid Whole Home network - I am using the SWM8 to diplex three receivers (6 tuners) to which I cannot get a second line. Using ethernet with those receivers - right now I am using Eagle 2100LX diplexers - I know they don't power pass 2MHz on satellite leg, I have NAS diplexers ordered -

My other receivers (11 tuners) have separate coax for off-air and are connected to the SMW16 using DECA (HR34 serves as BB DECA for those receivers).

Two separate SWM systems bridged at the router. All receivers sync, all receivers see each other, all receivers MRV.)

But I digress...This part really deserves another thread, and is somewhat off topic here...*_


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## veryoldschool (Dec 10, 2006)

I'm not sure the 24 volt "brick" has the wattage.
A SWiM-16 has problems with a 36 watt PI.


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## hidefman (Dec 16, 2006)

veryoldschool said:


> I'm not sure the 24 volt "brick" has the wattage.
> A SWiM-16 has problems with a 36 watt PI.


Yep. I am thinking the same thing. I am going to use the two 29 volts power inserters for each SWM. (Listed at 43.5W)

On the SWM16, I will use the power port.

On the SWM8, do you recommend using the SWM1/PWR port? or the legacy 3 port for connecting the power inserter? I can use either, as I can connect my three receivers (6tuners) to SWM2 port via green label splitter.


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## veryoldschool (Dec 10, 2006)

hidefman said:


> Yep. I am thinking the same thing. I am going to use the two 29 volts power inserters for each SWM. (Listed at 43.5W)
> 
> On the SWM16, I will use the power port.
> 
> On the SWM8, do you recommend using the SWM1/PWR port? or the legacy 3 port for connecting the power inserter? I can use either, as I can connect my three receivers (6tuners) to SWM2 port via green label splitter.


On the SWM8, I like the #3 legacy option.


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## hidefman (Dec 16, 2006)

Ok, worth a try! Just looking at the specs, the 24volt brick is also rated at 43.5W, but it is being asked to power a SWM8 + SWM16.

I'll post back if my problem goes away, and then we can also add that the E-2 Expander does NOT have enough power to drive two SWM16s using only the 24 volt power supply.

Again, only temporary until the splitters and NAS diplexers come in...

Then I'll go back to the SWM's in parallel without the E-2 Expander.

Thanks VOS. You're okay with how I have configured my hybrid Whole Home setup?


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## veryoldschool (Dec 10, 2006)

hidefman said:


> Thanks VOS. You're okay with how I have configured my hybrid Whole Home setup?


If it's working.... isn't that the point?


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## hidefman (Dec 16, 2006)

Ok. Sorry to bother.


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## hidefman (Dec 16, 2006)

Update: With my E-2 Expander configured with (1) SWM8+ (1) SWM16, I was having trouble with one receiver/DECA set-up on the SWM16 side. I thought it might be low voltage/wattage from the single 24 volt power supply. Even after I changed to separate power inserters for the SWMs, my 775 & 771A problems persisted. I even swapped the SWM and off-air coax cable and rebooted, but the error codes remain.

Until I simply just relocated the suspect receiver to another location on the SWM8/ethernet side. Problem solved. All 7 receivers still see each other on both the DECA and the ethernet sides... all MRV functions normal.

I think this one receiver does not like the 60 ft run. Swapping cables didn't matter... DECA module kept losing sync. 

At any rate, I don't think it is the power supply. After looking at the rating for the single 24 volt brick, it is rated at 49.5W.

So, I cannot conclude the Expander can or cannot drive two SMW16s one the one power supply provided.

Heat sink, spacing and other heat issues remain.


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## ewing453 (Oct 22, 2008)

I have been using the E2 with the included power supply and 2 SWM16s for over a month now without problems. They did appear to get pretty hot so I put a 12v CPU case fan above them. They are much cooler now than the single swm was before. This may not work for everyone, but the swm expander could not be cleanly installed in my rack.


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## veryoldschool (Dec 10, 2006)

ewing453 said:


> I have been using the E2 with the included power supply and 2 SWM16s for over a month now without problems. They did appear to get pretty hot so I put a 12v CPU case fan above them. They are much cooler now than the single swm was before. This may not work for everyone, but the swm expander could not be cleanly installed in my rack.


The expander is merely a block of splitters, so addressing the heat, as you have was what was needed.


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## Jodean (Jul 17, 2010)

Jodean said:


> I was just sent this for an mdu project. First board of four in this building.
> 
> I see no heat issues that would arise from an E2, the swm 16's are over an inch apart, dont see how that would effect cooling, esp when they are indoors at 70 degress constant.


Building one going on month 5 now, no issues. Building two going on 2 months. going to be 10 building all together so should be a great test for this type setup. Will report any burnt up swms.


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## veryoldschool (Dec 10, 2006)

Jodean said:


> Building one going on month 5 now, no issues. Building two going on 2 months. going to be 10 building all together so should be a great test for this type setup. Will report any burnt up swms.


Sometime around August might be when heat could be a problem.


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## slice1900 (Feb 14, 2013)

I'm using splitters so I can't comment on the heat from stacking SWM-16s. I used standoffs to keep them away from the wall they're mounted on to improve airflow and allow routing cables underneath them since I've got a pretty small area with a TON of coax running around.

As far as the discussion about powering them goes, I'm using a single 24v 2.08A Sonora power supply to power both my SWM-16s per Sonora's configuration guide and it is working flawlessly. Per their measurements the SWM-16 draws a bit over 17 watts (depending on whether you supply 21, 24 or 29 volts - if you want to minimize heat, don't give it 29 volts) An SL5 LNB draws either 9 or 12.5 watts, it isn't really clear when they say "200ma" for the 18v line if they mean 200ma @ 18v or 200ma @ 24v, but whichever you only pay that once no matter how many SWM-16s you have paralleled off from it. So it makes sense that a single PI-29 putting out 43 watts can't power two SWM-16s, but the ~50 watts the Sonora supply puts out is definitely enough.

The PI-29 probably puts out higher voltage than the SWM-16 needs since it will in some cases be used by some people for inserting power over an unknown distance over crappy RG-59 clad cabling that was already installed in their home, so the PI-29 was over-specced to supply more voltage and current than would ever be required over any cable length/quality that would otherwise work. If your power run is only a few feet you could surely use a PI-21 for one SWM-16, or really just about any decent 24v supply that puts out at least 1.25A.


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## veryoldschool (Dec 10, 2006)

slice1900 said:


> If your power run is only a few feet you could surely use a PI-21 for one SWM-16.


Some have had problems with the 21 volt PI trying to power a -16, so "surely" is a poor choice.


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## veryoldschool (Dec 10, 2006)

slice1900 said:


> As far as the discussion about powering them goes, I'm using a single 24v 2.08A Sonora power supply to power both my SWM-16s per Sonora's configuration guide and it is working flawlessly. Per their measurements the SWM-16 draws a bit over 17 watts (depending on whether you supply 21, 24 or 29 volts - if you want to minimize heat, don't give it 29 volts) An SL5 LNB draws either 9 or 12.5 watts, it isn't really clear when they say "200ma" for the 18v line if they mean 200ma @ 18v or 200ma @ 24v, but whichever you only pay that once no matter how many SWM-16s you have paralleled off from it. So it makes sense that a single PI-29 putting out 43 watts can't power two SWM-16s, but the ~50 watts the Sonora supply puts out is definitely enough.


Let's look at this a bit more.
The LNB is powered by either 13 or 18 volts. Even Sonora only raises this to 14 & 20 volts with their polarity locker.
With 4 coax @ 200ma each this is 12.4 watts
A SWiMLNB or SWM8 can be powered by a PI 21 @ 25.2 watts.
25.2 - 12.4 [LNB] = 12.8 watts
The older PI 29 is 36 watts, which works with a SWiM-16.
36 - 12.4 = 23.6 ÷2 = 11.8 watts/SWM stage.

The newer PI29 has been increased to 40.6 watts
40.6 - 12.4 = 28.2 ÷2 = 14.1 watts/SWM stage.

The PI21 @ 25.2 watts would be: 6.4 watts/SWM stage and this doesn't work.

The Sonora 50 watt PI would be: 50 - 12.4 = 37.6 ÷ 4 [2 SWiM-16s] = 9.4 watts/SWM stage.
Sonora tends to expect all of their products to be used, so with the polarity locker powering the LNB, the 50 watt PI would be 12.4 watts/SWM stage.

Maybe a SWiM works with 9.4 watts/stage, but it doesn't with 6.4 watts, and it seems all the others are designed for about 12 watts/stage.


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## slice1900 (Feb 14, 2013)

I'm not sure what this "SWM stage" you're talking about is. It looks like you're working backwards from the rated output of the power supplies Directv provides to calculate how much power each 8 tuner output requires? The PI-29 is unregulated, so they are going to have to build in a bigger safety margin versus a quality regulated supply like Sonora's. I've had problems with unregulated supplies in various roles over the years so I avoid them like the plague for anything I consider important.

In addition, Directv would have to oversize the supply to account for a fair bit of potential line loss since someone may locate a PI-29 next to a receiver that's too many feet of crappy RG-59 CCS house wiring away from the SWM-16, with possibly some couplers or other ugly stuff in the mix. Rather than trying to calculate the maximum power a PI-29 may provide I'm going by the measured power draw of a SWM-16 per Sonora's doc, which I also verified with my Kill-A-Watt meter. I can't measure the actual draw of the SWM-16 with it, only that of the power supply which powers it, which means it'll read higher because power supplies aren't 100% efficient.

I'm not sure if it is super accurate for small draws like this, but it showed 23 watts with the PI-29 and 20 with the Sonora supply (with the LNB powered by the other switch at the time) I measured 54 watts when I had two SWM-16s powered by the PS242000A, which would include LNB power. I also measured the WB-616 for the heck of it and found it drew only 7 watts using its own power supply. The PS242000A outputs 2.08A @ 24v and is rated to draw a maximum of 58.6 watts, so there's a good safety margin with my measurement of 54 watts. Here's a link to the doc I'm working from:

http://www.sonoradesign.com/images/POWER_sheet.pdf

You're right that Sonora typically tends to assume that everyone is using stuff like polarity lockers, amps and equalizers, but in this document they don't appear to be assuming anything but a direct connection to the LNB. They don't try to sell you the polarity locker until page 15 :lol: It is sold as a solution for having a lot of SWM-8s with 22khz tones interfering (that might be a problem if some are powered by an online UPS I guess, but with utility power I'm skeptical this can happen) Anyway, even if you were using a polarity locker, unless it were _separately_ powered, it still powers the LNB and would still count against the output of the power supply powering the SWM-16s and polarity locker.

On page 2 of their document they discuss SL5 powering and state it employs current management which limits the draw of 18v lines to 200ma and 13v lines to 50ma. Worst case assuming they are talking about current draw @24v it is 500ma or 12 watts. Your figures with 200ma at the target voltage on all four lines frankly makes a lot more sense to me unless someone knows of some reason why it would draw less on 13v, so I'll use your slightly higher figure of 12.4 watts.

On page 14 it discusses PS242000A powering SWM-16s, and shows the current draw measured at different voltages (17.3 watts @ 24v) One configuration shows two SWM-16s powered by one 24v supply, with two more SWM-16s along with a 105ma fan (@24v = 2.52 watts) powered by another 24v supply. For the second configuration with the fan, it notes that "NO SL5 powering is allowed with this configuration". If you do the math you see that extra 2.52 watts from the fan pushes it _really_ close to the edge assuming the LNB is drawing 12.4 watts, or even if it draws only 12 watts. Too close for them to be willing to support that configuration, I guess!

I'm not sure what would happen if you connected your SWM-16s using dual power passing splitters that are not diode steered like mine. If they both tried to power the LNB perhaps they could try to draw too much power and it wouldn't work, I'm not sure. The SWM-E2 expander solves this by passing power from only one SWM-16, so it wouldn't be a concern there.

But you're absolutely right that the PI-21 couldn't power a SWM-16, given that it outputs only 25.2 watts. With 17.3 taken by the SWM-16 you'd have less than 8 watts left, which isn't enough to power the LNB. I didn't realize the PI-21 had so little power, I was under the impression the PI-21 and PI-29 output the same amperage at different voltages, but I can't remember where I got that obviously mistaken idea. A 20 or 21 volt supply can power the SWM-16 (over a short run where voltage drop isn't a concern) but not the PI-21, it doesn't have the amperage required.


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## veryoldschool (Dec 10, 2006)

slice1900 said:


> I'm not sure what this "SWM stage" you're talking about is.


I used "stage" for "a SWiM" as they're made up from the same SWM8. The -16 is merely two SWM8s in one package, where both share the power input, but each are independent, so call them a stage or section for this "block".

Their listed power for the SL5 just doesn't make sense. 
16 VDC min is for the switch of the SL5 to select the right LNB/SAT.
200 mA seems reasonable from other docs.

The 50 mA doesn't because both of these are still needing to power the same load as the 200 mA lines.

Two PIs in parallel would be just like two batteries, where each would output half the amperage over a single.

The dual power passing splitter "issue" comes from the 22 KHz tone. "In theory" these could be out of phase and cancel as addressed on pg 15. 
I want to call this a myth, because there never has been a reported case that this was a problem, but "theory says" it could, so I won't.

Pg 14, 17.6 watts for a SWiM-16 may be a good value, as it would mean roughly 9 watts "per stage".

I seem to remember power supplies working best at 80%-90%, so there should be some headroom between the load and the rated max output.

The fact that they "don't allow" a 2.5 watt fan and power the LNB, suggest [to me] they're split hairs a bit finer than they should have.

As for the use of crappy RG59 between the PI & SWiM, this isn't approved, so I doubt it was a design parameter.
Using RG59 was to be only on the RF lines when it couldn't be replace with RG6.


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## slice1900 (Feb 14, 2013)

veryoldschool said:


> I seem to remember power supplies working best at 80%-90%, so there should be some headroom between the load and the rated max output.
> 
> The fact that they "don't allow" a 2.5 watt fan and power the LNB, suggest [to me] they're split hairs a bit finer than they should have


Switching power supplies today are subject to various regulations/incentives for them to be 85% efficient. That doesn't mean they run best at 85% load, but that they output 85% of their input AC power as output DC power throughout their entire typical operating range. A decade ago it was typical for crappy supplies to be well under 50% efficient throughout much of their operating range and some were never even 70% efficient at any point. Since there are so many of them around (almost every CE device has one these days) a significant amount of power was getting wasted which prodded governments into action.

If you look at the Sonora supply's 58.6 watt max AC draw and 49.92 watt (2.08A * 24v) DC output it comes out to almost exactly 85%, though from the numbers I measured it is actually better - but Sonora does list the 58.6 watts as worst case number used for QC. I don't have the figures for the PI-29, I would guess it is around 85% efficient based on my measurements.

I don't agree that the addition of 2.5 watts pushing it over the edge means they're splitting hairs, however. If you have a device that's going to provide about 50 watts (just under) and its regulated, so it actually _will_ produce that much, you decide how much headroom you want and base things off that. If you say "let's give a 5% margin to allow for manufacturing defects in the SWMs, LNBs or power supplies, and two SWM-16s and a SL5 LNB fall just under that, even a half watt might be "too much" if it pushes you over that. They could have a 100 watt supply and if they decided they wanted a 50% margin and everything they needed drew 49.9 watts, even a quarter watt could push them over the edge, despite being ridiculously generous with their margins.


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## veryoldschool (Dec 10, 2006)

slice1900 said:


> If you look at the Sonora....


I think I've found the answer.

It's not an issue of watts, but current limiting.

"The current use for supply 2 is (2) x 720 mA + 105 mA (fan) = 1.5 Amps. NO SL5 powering is allowed with this configuration."

If the LNB is 500mA, as Sonora says earlier, this would be 2.045A

The SL5 + 2 -16s = 1.94A

You may not feel Sonora is splitting hairs a bit too close, but with a max output of 2.08A, and 140mA below is "OK", but 35mA above isn't, well it sure looks like a very fine line to me.


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## HoTat2 (Nov 16, 2005)

Humm ....;

So let me get this straight, according to Sonora anyway.

The legacy SL-5 LNB draws a constant 200 ma nominal current between 20-16 v control voltage supplied to the 18v/18v 22Khz (even) signal connections and 50 ma nom. on the 13v (odd) connections (no voltage range given for 13v)?

Yet regarding SWiM applications it seems the the PI or power adapter actually behaves like an "auto-ranging" constant power output supply when powering a SWiM-8/16 or SWiM LNB like so? ...










Where "P max" refers to the required power of the SWiM(s) (plus LNB power for the external MS).

Just having trouble trying to make sense of some of what Sonora is claiming here in the documents.


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## veryoldschool (Dec 10, 2006)

HoTat2 said:


> Humm ....;
> 
> Just having trouble trying to make sense of some of what Sonora is claiming here in the documents.


Don't feel like "the Lone Ranger". :lol:
for the SL5, the max current draw of 500mA seems reasonable. 
In a legacy system 350mA is a common spec for switches.
The LOs all get powered and "I'd guess" the amps do to.
This works with the 13 volts, so roughly 6.5 watts, and the 18 volts is just used for switching.

As for what they measured for the SWiMs, it isn't clear to me if there's a change between one tuner or all eight being connected. :shrug:

I don't know what's inside a SWiM, but due to cost, I'd tend to think they simply have voltage regulators for the different voltages needed.
This would sort of match the current limit of the PIs.


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## slice1900 (Feb 14, 2013)

Drawing more total power (measured in watts) when supplied with more voltage makes sense, since DC to DC stepdown converters waste more energy in the form of heat the bigger the required voltage drop. Supply a SWM module with 29v and it takes a little bit more power than at 24v and that additional power is lost as additional heat. Supply it with 20v and it takes a bit less - but just a bit, those concerned with their SWM-16 getting hot probably aren't going to notice the 0.4 watts less heat it would radiate on a 20v supply versus a 29v supply unless they're shooting it with an IR thermometer.

There are different types of DC to DC stepdown (i.e. buck) converters available. Linear regulators are the cheapest, but least efficient. As the name implies, there is a linear relationship between the voltage drop and the energy loss. Then there are the various classes of switched mode converters, which can be almost as cheap and inefficient (as almost all wall warts until recently) to relatively expensive and efficient (as in the VRMs built into modern CPUs to provide 32 very precise levels of voltage for power management) And surely some high end stuff I'm not familiar with.

The one advantage of linear regulators, aside from being cheap, is that they're very low noise, something you'd be interested in when working with a weak satellite signal. To supply 13v and 18v to the LNBs wasted power from linear regulation wouldn't be too much of a problem. It would be rather wasteful for the 3.3v supply the SWMs would surely need for the electronics, since a 29 (or 24 or 20) volt supply dropping down to 3.3v via linear regulation would waste almost as much power as the electronics consume. Since electronics only need a few watts, maybe you don't care about wasting a few more in exchange for less noise.

On the other hand, if they didn't care so much about noise or didn't think it would be a problem, they could use VRMs like VOS suggested, similar to the ones used on PC motherboards except working at higher voltages. In that case, because they dissipate a lot of heat in a small area, you'd need to build your module to look like a heatsink. WIthout fans as in a PC case, you need a lot of mass and area to spread out the heat.

Based on the very small drop in power draw between a 24v and 20v supply when compared to the relatively much larger drop between 29v and 24v, and the construction of the SWM8/16 case itself, VRMs seem most likely.


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## HoTat2 (Nov 16, 2005)

OK, thanks for the responses;

Its just what I was trying to get straight on is the principle Senora is apparently describing that powering a legacy LNB results in approximately a constant current drain per line (200 ma or 50 ma) within a certain voltage range (20-16v for even and ?-13v-? for the odd).

Whereas when powering a SWiM, the PI or power adapter adjust its output voltage/current ratio (again within limits) to deliver a relatively constant power to a SWiM multiswitch, whether it be the standalone external type or integrated one in the LNB.


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## slice1900 (Feb 14, 2013)

The document states that "LNBs employ current management to minimize the current carried per coax." The LNB needs power for itself, which it can only draw from the four coaxes connected to it. For reasons having to do with Ohm's Law, it would be preferable that it draw power from more than one coax at a lower amperage versus drawing all operational power from a single coax at a higher amperage.

The document doesn't state that the LNB draws a _constant_ 200ma from the 18v lines, but it does imply that. If it does so, it is likely utilizing constant current diodes, which would always draw the current they are designed for, never more, never less, independent of voltage. This would allow it to limit the draw on any one coax to a set value. It would then use a linear regulator to step down to whatever voltage it requires to power itself, since one would expect that introducing as little noise as possible is one of the primary design goals of an LNB.

The document describes a 16v minimum on the 18v lines but does not list a minimum for for the 13v lines. If Sonora's document is correct about the 13v lines drawing only 50ma, they probably aren't used for power, but for signaling only. When the 18v lines fall below 16v presumably there isn't enough power at the linear regulator's input to produce the output power required for the device's operation.


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## veryoldschool (Dec 10, 2006)

slice1900 said:


> If Sonora's document is correct about the 13v lines drawing only 50ma, they probably aren't used for power, but for signaling only. When the 18v lines fall below 16v presumably there isn't enough power at the linear regulator's input to produce the output power required for the device's operation.


Given that the SL5 must work with only one coax and using only 13 volts, Sonora's testing isn't correct "for all cases".
This is sort of Sonora's problem with their testing/spec sheets.


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## slice1900 (Feb 14, 2013)

Perhaps this is the source of the discrepancy between the figures Sonora provides and what you said with all four LNB outputs drawing 200ma. They mention that it is current limited to a total of 500ma, so could be that any of them are capable of drawing 200ma if they're the only one (or two?) in use, but perhaps when there are four it arranges things so the 18v lines draw 200ma and the 13v are limited to 50ma to keep the total draw at 500ma.

I don't know enough about how it works to guess whether it would need less power if there is only one output active. It seems reasonable, but I have no real idea. The document discusses a single LNB 95* dish and says "LNB current is typically less than 200ma", so I guess those aren't current limited like the SL5. If someone had a few multimeters lying around to hook up to the lines running to an SL5, they could do a little testing and figure out what it draws under what circumstances, and what the minimum and maximum total draw is. Not that it really matters to anyone but the terminally curious such as ourselves.

Sure would be nice if there was a technical manual available for LNBs and switches, so it wouldn't be down to a bunch of speculation and guessing


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