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Guest Message by DevFuse

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When one SWiM isn't enough


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68 replies to this topic

#61 OFFLINE   veryoldschool

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Posted 16 March 2013 - 04:16 PM

I could make sweeps with spectrum analyzer and post them here, if someone will throw away "old" SWiM LNBF or SWM-16 (to connect it to my AU-9 LNBF) ;) ...

I might have a spare SWiM LNB to lend but I want pictures. :lol:
A.K.A VOS

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#62 OFFLINE   P Smith

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Posted 16 March 2013 - 04:25 PM

I promised !

#63 OFFLINE   AntAltMike

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Posted 16 March 2013 - 06:09 PM

Several years ago, someone posted supposedly "exact" SWM center frequencies, and they actually had digits to the right of the decimal point, so if that post was accurate ( and I recall it was from a regular contributor here), then describing the spacing as 102 MHz is "more exact" than is calling it 100 MHz spacing, but it is not absolutely exact.

I use a field-grade portable spectrum analyzer with an 8 MHz wide bandwidth when I infrequently service SWM systems. Unfortunately, the displayed wave form is the intermediate frequency waveform that is the composite of the frequency shifted transponder signal and the local oscillator, so I can't tell much of anything by looking at one.

Because of the AGC, I can't even peak a dish that way. I have to remove the SWM and temporarily install a WB or whatever those LNBs are popularly called, peak the dish, and then reinstall the SWM.

I remember a few years ago seeing that some of the Ka band transponder center frequencies posted on Lyngsat were spaced further apart than were others, so if anyone with a spectrum analyzer on his hands takes it upon himself to first determine which programs are carried on which transponders and then selects programs from different width transponders and then looks at and compares the shapes of the different SWM intermediate frequency waveforms, he might learn something useful, or he might find that the narrowly loaded ones and more widely loaded ones look about the same on the spectrum analyzer screen because the waveform is overwhelmingly shaped by the local oscillator component of it.

Insofar as picking 102 versus 100 MHz for spacing is concerned, since DirecTV has that IF bandwidth available and since it is not artificially constricted in its engineering by any round decimal values, they may well have done some complex engineering analysis regarding the development of intermodulation byproducts and have determined that within the bandwith parameters that they have, that 102 MHs spacing is simply optimal for minimizing them. I have previously been told that the decisions to invert the upper L-band intermediate frequencies and the decision that NAS had made in its earlier versions of multisatellite destackers to use a different frequency offset than DirecTV favored was based on such engineering considerations.

Edited by AntAltMike, 17 March 2013 - 02:57 PM.


#64 OFFLINE   veryoldschool

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Posted 16 March 2013 - 06:27 PM

Might be time to start up another thread as this thread is about using more than one SWiM and ways to combine the DECA signals between them.
A.K.A VOS

#65 OFFLINE   SomeRandomIdiot

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Posted 17 March 2013 - 11:07 PM

I can attest to that :lol:
Spend the money on the correct diplexers.


I have 4 NAS here that I previously ordered. Just trying to grasp why they are needed if I have an extra leg on the 4 port splitter to take a feed off of and combine. As thus, it has nothing to do with costs. Just seems that taking the diplexer out of the equation would improve signal loss.

Also, fwiw, the SWiM32 seems to be running much cooler than the SWiM16s that were replaced. In Air Conditioned room where the SWiM16s were measured at 116F via a Fluke IR Thermometer, the SWiM32 is only running 94F. Its unknown whether this is a result of larger surface area, the different supplier or the fact that I am not powering the LNBs through the SWM32s (it would seem that might generate some internal heat in a SWM8 or SWM16). Whatever the reason, its 22F cooler.

As VOS noted on another thread (somewhere on site), that still does not answer questions about life expectancy, but I would hope lower heat = longer life.

Edited by SomeRandomIdiot, 17 March 2013 - 11:19 PM.


#66 OFFLINE   HoTat2

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Posted 18 March 2013 - 04:55 AM

I have 4 NAS here that I previously ordered. Just trying to grasp why they are needed if I have an extra leg on the 4 port splitter to take a feed off of and combine. As thus, it has nothing to do with costs. Just seems that taking the diplexer out of the equation would improve signal loss. ...


The diplexers are necessary, in fact indispensable for this application, to separate and isolate the SWiM satellite signal paths from the DECA (MoCA) network signal paths.

They allow each of the four SWiM-8 circuits (two SWiM-16s) comprising 9 RF carriers + a 2.3 MHz control signal to remain confined to one of four isolated signal paths, while the paths for the DECA network signals are combined into one overall cloud.

#67 OFFLINE   veryoldschool

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Posted 18 March 2013 - 09:26 AM

Just trying to grasp why they are needed if I have an extra leg on the 4 port splitter to take a feed off of and combine. Just seems that taking the diplexer out of the equation would improve signal loss.

Add a 475-625 MHz bandpass filter to this and it would work.

Actually this isn't quite true either.

You could connect the NAS diplexer to splitters on each of the SWiM-16s and terminate the unused port. This would bridge the DECA between the two, but the losses would mean you couldn't go from one SWiM output through the crossover to the other output and then do the same on the other SWiM-16.
The only combination that would work would be using only 2-way splitters and keeping the coax runs no longer than 50'

Edited by veryoldschool, 18 March 2013 - 02:42 PM.

A.K.A VOS

#68 OFFLINE   Robster138

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Posted 30 July 2013 - 11:55 PM

Very awesome!



#69 OFFLINE   ljg1118

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Posted 12 August 2013 - 01:06 PM

Is there currently  any workaround to the limit of 10 Clients per DVR, or a work around to select which clients a DVR can be shared with? 






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