Stackers/Destackers

dahamsta

Lot of mixed information out there about these, lots of people recommending them as a solution to someone that wants Sky+ with only one satellite feed, but confusing comments about issues with polarity and the possibility that you may not be able to record certain programs while you're watching certain other programs.

Anyone care to explain to this TV tech innocent how these things are supposed to work, and more importantly if they do actually work or not in practice?

adam

Zaphod

http://www.parabolic.co.uk/catalog/product_reviews_info.php?products_id=193&reviews_id=29

dahamsta

Thanks Zaphod, but that's just reprinted sales guff. Has anyone actually fitted or used one of these?

adam

parsi

Conrad (www.conrad.de) have loads of these in different flavours see

http://www1.conrad.de/scripts/wgate/zcop_b2c/~flN0YXRlPTIzMjA2Njc4OTc=?~template=PCAT_AREA_S_BROWSE&glb_user_js=Y&shop=B2C&p_init_ipc=X&~cookies=1

They call them "Sat-verteiler" They seem to be touted a lot for apartments or similar installations. They don't sell them as a "wonder item" just as a simple product without any special claims..

dahamsta

Does anybody read posts around here any more, or is the de facto standard to quickly scan the thread title and post something whether it's relevant to the actual enquiry or not? I'll try once more:

Has anyone actually fitted or used one of these?

adam

Capt'n Midnight

never knew they existed till now - looks a bit like Eircom Pairgain - two signals down one wire by frequency shifting one of the signals. If you can run two cables then ignore it.

"the small Stacker box is mounted directly behind the LNB and comes with two inputs (5-2,150 MHz and 950-2,150 MHz) and one output (5-3,550 MHz)"

the 5-2150 is normal TV and satellite range.
The second imput satellite only? is shifted up to 2150-3,550 and shifted down at the other end. Cable losses are worse at higher frequencies and the mux/demux / extra connectors / amps will all add some noise, so my guess is that you would need top notch cable to benefit fully.

If there was any way you could run a second cable that would be a better solution 'cos you are going to need a dual or quad lnb anyway.. Sounds like it does someting completely differently to diseq and passive or "master/slave" switches/ splitters.

dahamsta

It's a communal dish, LNBs isn't a problem. If the option of two cables were available, I wouldn't be asking about stackers/destackers.

adam

Zaphod

dahamsta wrote:

Thanks Zaphod, but that's just reprinted sales guff. Has anyone actually fitted or used one of these?

Not quite sales guff. It's a reprint of a review conducted by Christian Mass from Tele-Satellite magazine.

The review answers your question about how Stackers actually work ("the Stacker module places the individual IF segments in line with each other"), how well they perform in practice ("The signal loss in the IF range is a mere -4dB resulting in very little reduction in signal quality."), and it addresses you concerns over polarity + band selection ("It didn’t matter if the first receiver was in the upper band or the lower band nor did it matter what polarization was in use, the other receiver could do whatever it wanted to").

dahamsta

It didn't answer the primary question though (do they actually work or not), in fact it introduced the aforementioned confusion. For example, your last quote seems to suggest that is can handle two channels at the same time, whereas this...

When used on a PVR with two tuners (like the SKY+ Digibox), one program transmitted in vertical polarization in the upper band can be recorded while at the same time a second program in (eg.) horizontal polarization in the lower band can be watched from the same satellite independent of the first program.

...seems to suggest that it can't handle channels with different polarizations at the same time. Hence the thread.

I'm not trying to be difficult here, I'm just not getting the answers I was looking for, which is why I asked if anyone has actually installed or used one of these. Probably not I guess.

adam

Zaphod

dahamsta wrote:

It didn't answer the primary question though (do they actually work or not),

Are we reading the same review?

The quote you refer specifically states that you can record + watch 2 different polarisations at the same time i.e. 1 is Vertical, high band and 2 is horizontal, low band.

Capt'n Midnight

dahamsta wrote:

It's a communal dish, LNBs isn't a problem. If the option of two cables were available, I wouldn't be asking about stackers/destackers.

adam

Can your SKY box see all the bands at the moment ?

If communal LNB is one of those fancy ones (can't remember the name) where each of the 4 outputs is of a separate band / polarity AND all four go into another box (again with the name) that has like 8 inputs, where any of the 8 would be connected to appropiate LNB output so that the receiver behaves as if it had a single LNB then it should be easy enough to do. All you do is take 2 of the 8 inputs and use the stackers to put them down your cable and split at the other end.

Otherwise if two people are sharing a quad LNB then each can use two outputs.

Otherwise it gets trés messy 'cos digiboxes don't support diseq - depends on the existing setup

[no idea what the quality is like on them though.. ]

dahamsta

Zaphod, that was a misstatement, I meant to say that it "seems to suggest that it can't handle channels with [the same] polarizations at the same time".

Capt'n Midnight, like I said in the first post, I've never really looked into TV tech, so I really haven't a clue what you're talking about.

adam

Capt'n Midnight

Capt'n Midnight wrote:

Can your SKY box see all the bands at the moment ?/QUOTE]
What is in place at present or what is allowed - as that will dictate your options.

The way I understand it there are probably two likely options

If you are allowed put up a dish but are limited to the existing cable to it then you could have a sky and a sky+ box running off the same cable to a quad or dual lnb - with the (de)stackers if the run isn't too long

If there is already a disk and it has a intelligent-splitter box with a cable for each appartment then you would need to use two of those cables into the (de)stacker. - there may not be a spare one and you may also need to get them to get a bigger splitter box.

hope that makes some sense

dahamsta

It's one single communal dish for a block of 56 apartments CM. The guy who installed it didn't mention a cable shortage, so it should be possible to use the stacker/destacker. However he's never installed one before so he doesn't know whether it'll work, or the level to which it'll work, so that's why I'm here. It doesn't look good though, no-one seems to have actually used one.

adam

Capt'n Midnight

http://www.satelliteonline.co.uk/commercial_systems.htm
http://store.securehosting.com/stores/sh200904/shophome.php?itemprcd=multiswitch

the yoke on the roof is called a multiswitch apparently - the one above would do up to 16 outputs so there are several up there or a whopping great big one. I've no idea what the setup is at your place but 64 way sounds plausible (ie. 56 cables and 8 spares - so get there before the neighbours)

You could look for a company that does both multiswitches and (de)stackers and ask them a "pre-sales question" and see what they say.

But someone out there must have tried it out..

Zaphod

dahamsta wrote:

Zaphod, that was a misstatement, I meant to say that it "seems to suggest that it can't handle channels with [the same] polarizations at the same time".

The quote doesn't suggest that either. The reason there is such an emphasis on the ability to watch channels with different polarisations (and bands) in the review is that it is technically more difficult to accomplish that over one cable, than it is for 2 channels of the same polarisation - you need to handle and isolate the different 13v and 18v polarisation switching signals at the destacker and stacker ends. In fact, if you just wanted to watch 2 channels with the same polarisation, you wouldn't even need a stacker - just split the cable at your end and block power-passing from one of the receivers. The stacker is designed to handle 2 channels simultaneously, regardless of what polarisation or band they are in. If it couldn't do that, it would be completely worthless as a product.


When you mentioned initially that you had read confusing comments about problems with polarity etc., where exactly did you read this? Any feedback I have seen on stackers in other satellite forums has been positive.

It's one single communal dish for a block of 56 apartments CM. The guy who installed it didn't mention a cable shortage, so it should be possible to use the stacker/destacker.

I think this is potentially a far bigger obstacle than any worries you have about the stacker. For a block of 56 apartments, a single multiswitch won't suffice. At the very least, they are using a set of cascadable multiswitches, or more likely a tap-off setup to accommodate such a large number of outlets. So you need to be certain that there is a spare multiswitch port or tap-off where your coax cable terminates at the headend. If there isn't, then it's academic questioning whether a stacker will work or not.

Zaphod

A few more links which might be of interest.

Sky+ and stacker:
http://www.satellites.co.uk/php-bin/forum/showthread.php?t=42633

What Satellite magazine sell reprints of their reviews - see Accessories -> Janhannsson (sic) Stacker Dec-02
http://www.wotsat.com/reprints.html

Electroplus in Dublin stock stackers and would have experience with the installation of large systems for flats etc.
http://www.electroplus.ie/

The Johansson FAQ:
http://www.johansson.be/htmen/ovv_prod_faq.php?prod=&debut=10

Finally going somewhat off topic, everything you ever wanted to know about multiswitches but were afraid to ask:
http://www.satellites.co.uk/php-bin/forum/showthread.php?t=41947