Multiswitch setup not working: what's wrong?

[clausius]

Hallo.
First here is a sketch of my setup:

The "multi-switch" is an EagleAspen DTV3x4 that should just do what i need: power both halves of the double LNB and select polH on one, and polV on the other thus receiving the whole band decoded in both polarization.
Then the tension at the output (received by the decoder) selects which polarization is fed to it.

Now my problem: not every possibile combination of channels on Decoder1 and Decoder2 does work.
For example (i have standard SKY decoders and bouquet) 210 and 410 together won't go (actually sky sport 3 and Rai Sat Gambero Rosso, italian SKY).
110,111,112 (FOX triad: fox, fox life, fox crime) on one decoder, and 210 on the other would.
I first thought of a problem on one of the lines coming down from the LNB (maybe half LNB gone) but then, changeing which went where on the DTV3x4, everything remained the same. (interchanged between the 17V and 13V)
So it should not be the LNB fried.
But then what else could be?
This setup should be able to drive a standard receiver in one room, and a SKY+ in another room.
As it is now not even 2 outputs are indipendent, let alone three.
Obviously, as well as sadly, using only one decoder everything works fine.
What can i do?
Thanks all.

 

[rolfw]

You need a Quattro LNB, plus a 5 in 6 out multiswitch unit, as you have four states of the LNB, horizontal Low and High, plus vertical Low and High.

 

[clausius]

For what i know the status you mention belongs to a kind of "old age" of sat-tv.
Nowadays LNBs feed the entire frequency range (not divided any more into high or low, which was the case of 4 output LNBs).
The only thing that is still splitted (for physical reasons: same frequency signals would interfere on the same cable) is the polarization.
In fact the only signal a decoder sends to the LNB is a voltage spanning from 14v to 18v; this tension provides both power to operate and polarization selection to the LNB.
Now the theory behind all this is:
if you got dual LNBs and one half is operated in Vpol and the other in Hpol, all the available signals are available on the two coax cables.
So an opportune circuit can mix them up and make them available at decoder's choice.
This is advertised on this site _http://www.starlink-dss.com/multiswitch.htm
as well as on many others like these
_http://www.broadbandutopia.com/viddis.html
_http://www.hometech.com/learn/dss.html

 

[rolfw]

You are incorrect, as European satellites require a 2 Local Oscillator LNB (Universal) to receive channels from 10,700 to 12,700, the setup you describe above is the legacy system for analogue only on Astra 19.2 and Hotbird, before LNBs started using 22Khz tone switching for upper and lower band.

http://www.sateuropa.co.uk/product_overview.asp?id=570&catid=1&subcat=11

I am presuming from your details that you are in Italy, but you are looking at websites describing setups for American satellite feeds.


PS. Depending on how many receivers you are going to ultimately connect and whether you require a terrestrial feed at each outlet, you may be able to use a quad or even Octo LNB rather than a multiswitch, I believe that there are quad LNBs available which accept a UHF feed for a diplexed outlet.

 

[clausius]

It's difficult to find such detailed informations, and i rely on what i can find.
My main problem is that i would like to have 3 (or maybe 4) indipendent decoders but i have only two coax running from the roof.
And this i can't expand so easily (would require some new holes, and the walls are new, and so on...)

 

[rolfw]

With your existing equipment you cannot do it, you could perhaps change the LNB to a quad and use a stacker/destacker to send two signals down one cable to give you three in total, but it is an expensive alternative.

There is new technology which will send four signals down one cable, but it requires significant investment and it will be a while before it becomes readily available.

PS. Is the LNB a dual or a twin, 1 h and 1 v output, or two universal?

 

[clausius]

It's a twin universal if i am not mistaken.
Anyway directly connecting two decoders to the two coax cables, they work good.
So the LNB should be a twin.

 

[rolfw]

OK, so really your options are limited, in that you need a quad or quattro LNB and a couple more cable runs into the house from the dish, or at the very least a quad LNB and a stacker/destacker, using existing cable runs.

 

[clausius]

Ok.
Thank you very much.
Would it be a problem for you to link me to some reference on this matter?
I'd like to understand a little more about all this.
For example why in USA it works and in Europe it does not.
Thank you again.

 

[rolfw]

The reason it works in the USA, is that they only use one band for say Dish 110W and 119W satellites , See the spec on a typical LNB for dish reception, note the smaller frequency range 11,700 Mhz - 12,700 Mhz of the FSS and BSS single band LNB.

A typical satellite in Europe uses 10,700 Mhz - 12,700 Mhz and requires an LNB capable of receiving a wider bandwidth, hence the birth of the Universal LNB, with 22 Khz tone switching between lower and upper band.


Here is a very limited description of the new single cable distribution technology.