Multiswitches and Fringe Area of 2D

[PaulR]

These, of course, simply don't work with a quattro as their is no voltage!

Quattros may not need (or even be fed) with 18v and the 25KHz signal but at least one of the feeds must carry 12v otherwise the LNB won't be powered.

What I don't know is whether it is only 1 line which is powered (or all 4) and, if so, which one it is!

 

[billnot]

Quattros may not need (or even be fed) with 18v and the 25KHz signal but at least one of the feeds must carry 12v otherwise the LNB won't be powered.

Yes, of course! !

I wasn't thinking straight.

 

[billnot]

Obviously different rules for different countries. How does attenuating a 2D transponder help? We need to boost as much as we can for 2D over here.

I've been thinking about this.
Something that's of great significance in this area is cross polar rejection. We have wildly differing reception conditions for the different Astra2 satellites.
In particular, the north beam transponders can be swamped by adjacent south beam and, to a lesser extent, 2D horizontals can be swamped by their vertical neighbours.

This leads to an odd situation with certain north beam transponders in that bigger isn't better. If all you wanted was to receive channel 4 24x7, you'd need a 1,5m dish and all would be fine. But most people have a 2,4m dish to get 2D. This actually degrades reception of C4. With my 3,1m dish, if I optimise for 2D I lose C4 for a couple of hours in the afternoon.

This is obviously due to the very powerful adjacent south beam transponders. These can be received with a 50cm dish here, so with a 3,1m they must be strong almost to the point of being too strong.

With 2D, the difference in strength between horizontal and vertical transponders is considerable. A 2,4m dish will get the verticals 24x7; with luck it will get the horizontals 12 hours a day.

When the attenuator is adjusted, then either 10773H (BBC2) or 12168V (Channel 4) is used as the test transponder. It can only be that the attenuator is minimising cross polar rejection.

I'm not 100% convinced about the role of the attenuator, but some installers use one as a matter of routine, and I couldn't see them doing so unless they thought it beneficial.

 

[PaulR]

It doesn't affect me as I'm right in the centre of the footprints but I have been musing about signal overloading on large dishes for some time. I have wondered why it doesn't seem to be an issue but, reading through, perhaps it does.

My thoughts go as follows:

Astra 2D is on low band and needs a large dish on the fringes. The others are on high band and don't. If you're using a multiswitch is there any advantage to, say, having a large dish with LNB for just the low band feed and a more moderate size dish for the high band signals?

Taking the thought further; as there appears, from what you say, to even be a difference between H and V you could have 3 different sized dishes for low band H, low band V and high band.

All theoretical of course and you could tell me to go away and lie down in a dark room but is anyone prepared to take the idea and run with it?

 

[billnot]

I
If you're using a multiswitch is there any advantage to, say, having a large dish with LNB for just the low band feed and a more moderate size dish for the high band signals?

I don't think it would work, for the reason that made me go ! in post no. 22 in this thread.

 

[PaulR]

Yes, but only if there isn't a 12v feed on all lines. As I said I don't know. Perhaps it varies from manufacturer to manufacturer? As a final thought, one could use in-line power supplies such as used to power TV aerial preamps - but only if they pass the higher frequencies of course!

 

[rolfw]

The in-line amplifiers that I have used with quad LNBs take their power from the receiver current to the LNB. These, of course, simply don't work with a quattro as their is no voltage!

Sorry just seen this, I've just set up a quattro LNB on the end of 100m of WF125 into a Triax multiswitch and four inline amps, the system works perfectly, with all amps being powered, have also used single line amps with Philips multiswitches.

 

[Zorba]

Where did you fit the inline amps ? Between the lnb and multiswitch ? I didn't know there was no voltage from multiswitch to quattro.

 

[PaulR]

I didn't know there was no voltage from multiswitch to quattro.

No, what Rolf is saying is that all 4 lines are powered.

 

[Zorba]

The in-line amplifiers that I have used with quad LNBs take their power from the receiver current to the LNB. These, of course, simply don't work with a quattro as their is no voltage!

True or false? I don't know

 

[rolfw]

Well it certainly isn't the case as far as I know on the multiswitches I have used, and that includes Hirschmann, Triax, Philips and Fracarro.

 

[billnot]

Well it certainly isn't the case as far as I know on the multiswitches I have used, and that includes Hirschmann, Triax, Philips and Fracarro.

Add Jesmay and Spaun to that list. My trusty multimeter tells me that there's 12v (more or less) on each input. I was wrong But not 14v or 18v, and I think that's significant.

But this isn't enough to power the in-line amplifiers I had lying around to play with (Tecatel and Global) - putting these in line killed all signals cold. That's why I'd assumed there was no voltage until it was pointed out to me that without 12v even a quattro simply won't work!

I was, of course, wrong !

The amplifiers I have must need 14v or more to work.

 

[PaulR]

I measured the voltages on a Labgear MS581E and the were just over 16v on the 2 vertical inputs and just over 18v on the 2 horizontal inputs.

Whilst 16v seems a little on the high side, presumably it really doesn't matter for a quattro. In which case why aren't they all the same voltage?

 

[rolfw]

I've never thought of measuring the output voltage, but do have a Fracarro unit in the van, so will get it out and measure it. I will also try and find out which make of inline amps I have used, as it may help someone.

 

[billnot]

Given the later replies, and for the sake of accuracy, the Jesmay gives 12v. I didn't measure the Spaun accurately, but I know it has voltage on all inputs (connect any one to the LNB and that one will work; therefore they must all have power.)

I am interested in trying some inline amps as, as I said earlier, my experiments with them have been unsuccessful. In my case, all I'm really trying to do is to improve the low - horizontal input. If I manage that, I'll have sorted a problem that's existed in much of Spain since 2D came into service.