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boatlover said:
I have a question about splitters.

I am going to be upgrading my system to SWM, whole home w/cck. My family room is pre wired (rg6) with 4 outlets around the room to make furniture arrangement easy.
These outlets are Daisy chained together using 1 output of the splitter to feed the wall plate and the other output to the next splitter/wall plates. The spacing between outlets is about 8 ft. Only 1 receiver will be used in this room. This has worked well with my old Dtivo as the wife can move the furniture and there are not cables all over the place.

If I use the green label splitters will this continue to work with a SWM setup?

Thanks Dave


veryoldschool said:
Nobody in the right mind would wire them this way.
In the simplest terms, a 2-way divides the power by 2, so:
first wall plate has 50%
second has 25%
third has only 12.5%
"and so on", reducing the signal by half each time.

As wallfishman has said, remove all the splitters and use barrel connectors to join the coax so you have only one wall plate connected.
Looks like I'm not "in my right mind".

The third and fourth wallplate each get one-eighth of the signal (12.5% splitter share, minus coax loss), just as receivers connected to an 8-way splitter get one eighth shares.

Not everyone is willing or able to run new wires in an apartment with finished walls. If the total coax length from the dish to the last wallplate is under 200 feet, this should work.

I just stumbled on this thread while searching for technical info on green splitter loss characteristics. Yesterday, I attended a seminar on installing the DRE2 system in hotels, and was was hoping to find something regarding the technical "wizardry" that gets green 4-way splitters output port isolation values of typically 14dB, versus the more typical -25dB published isolation value of common cable TV splitters.

Has anyone found a schematic for the internal construction of green labeled splitters? I am wondering if they diplex internally before splitting, and if the L-band isolation values are more normal.
 

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I don't see why Solid Signal is even bothering to publish the L-band frequency isolation. I only inquired about it because learning it might let me better speculate on how they developed lower isolation loss at cable TV frequencies.

The training seminar said that there was supposed to be no more than 45 dB loss at 600 MHz from any one receiver's satellite RF port to any others. Since we in the RF distribution system design business have never considered output-port-to-port to be a valid signal path, it never went into any loss calculations we did. Not only was it over 20 dB in off-the shelf hybrid splitters, which our loss budgets couldn't absorb, it was brutally non-linear across the channel, as evidenced by how ugly the analog pictures looked when developed from a signal that had passed the "wrong way" through a splitter, even if the signal strength, as measured by a signal strength meter on the +1.25 MHz visual carrier peak, was adequate.

You'd think that the splitters would be furnished with published 600 MHz, output-port-to-output-port loss figures for us to use in our seat-of-the-pants loss projections.

FWIW, in the master antenna distribution business, we used to sometimes used a component called a back matched tap, which served the same purpose as a directional coupler, in that it bled a small amount of signal off a trunkline and passed the rest. But one significant difference between the operational characteristics of a directional coupler and a back matched tap is that the back matched tap was non-directional, so while it functioned the same as the directional coupler when used correctly in the forward direction, it functioned differently when one connected it backwards. A backmatched tap has no dedicated input or output port. Both trunkline ports are simply labeled "thru".

If I used a -7dB directional coupler or a -7dB back matched tap to supply a wallplate, the signal coming out of that tap would be seven dB lower than that of the trunkline, whereas the signal portion passing through it would be about 2 dB lower. But if I backfed signal into that thru/output port, to send it upstream, while both devices would similarly pass it though to their input port, the tap port labeled -7dB on the backmatched coupler would still bleed off a flat, -7dB signal, whereas the tap port labeled -7dB on the directional coupler would be down 20 or more dB and non-flat, similar to the frequency response of a misconnected hybrid splitter.

I used to carry backmatched taps with me when upgrading wiring in old buildings where sometimes, when I was upgrading a wallplate, both wires were dead and unlabeled, so if I installed a directional coupler at that moment, there would be a 50-50 chance I'd be called back to swap the wires on it. The technical disadvantage of using the backmatched tap is that it slightly increased the intensity of any interference that a connection near the end of the line inadvertently injected into it.

But anyway, there are off-the shelf, 2-port directional couplers that are used to conveniently support 2 output residential wallplates, so I am wondering if it is similarly possible to develop 2 or more port backmatched taps, and if it is, then an 8-port backmatched tap that is designed to have -11 or -12 dB ports, with a terminating resistor on its anemic, thru port, should have about the same value "port-to-port" isolation as its tap value.

So what I'm wondering is, are these green labeled splitters really just back matched taps?
 

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My first search foray for a multi-port backmatched tap led me to this clunker, the Blonder Tongue V-2WS 2 port, backmatched terminating walltap. This device probably went out of production thirty years ago.

http://www.multicominc.com/active/m...talog/section_six/by_page/versatap_series.pdf

It is front illustration #4, rear illustration I, and spec-ed in the far right column.

Its existence tends to validate my speculation that multiport, backmatched taps are a proven circuit design. I have to go to work now, but will try to investigate back-matched-tap circuit design when I get home tonight.

NSC Distributing claims to have the Blonder Tongue V-2WS for $8.24, but a hobbyest probably couldn't meet their minimum order value.

Update: I just took another peek at the linked Multicom page of discontinued walltaps and see that there was also a product numbered V-2G-B (front illus #4, rear, "A") that was a backmatched multiport tap that was not line terminating, that permitted selection of port values of -12, -17 and -23 dB, and it was unshelded, making it convenient to analyze, and of course, since this was made before SMT, you can visually identify the component values. Each port would have two parallel resistors going to it, and if you left them both in circuit, the value was -12 dB, if you cut one it became -17 or if you cut the other, it became -23.
 

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veryoldschool said:
This is the limit of the Phy level loss.
Above this the Phy mesh rates start dropping.
An AOL phrase search for web pages containing the term "Phy level loss" located only one. It was buried in the resume of an Indian Professor of compuer science named Mukul Goyal. https://pantherfile.uwm.edu/mukul/public/bio.html

Searching for "Phy mesh rates" was more fruitful. There were two such pages found on the web. One was on DirecTV's own user forum and was posted back on August 8, 2010 by a tafiche, which is, or was, also the screen name of an infrequent contributor to this forum, but he (or she) hasn't posted here since August 11, 2010. http://forums.directv.com/pe/action/forums/displaypost?postID=10735485

The only other internet page located by the AOL search containing that term was here, and authored by... VOS. http://www.dbstalk.com/archive/index.php/t-201667.html

Several years ago, I remember searching out some arcane technical info and was initially pleased to see that my search had found over a dozen pages containing the search phrase, but was dismayed to then observe that nearly all of them were comments that I, myself, had authored. In fact one of the few that I didn't directly author, posted on a forum I had never previously visited, cited me as the source of its wisdom, saying something like, "and that's from AntAltMike, who I'm sure you all recognize."
 
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