Multiswitch advice

[Captain Jack]

I am a newbie to the multiswitch territory but I've got a Vision multiswitch with an Inverto quattro LNB. All connected up but I am a bit confused as to what various dB readings mean.

First is max B/A gain. My Ku LNB is connected to the A ports, so I am looking at max gain of 10dB or 8dB depending on which receiver port I am connected to.

In addition there are adjustable "pots" for each of the inputs, which I gather change the "gain", between 0dB and 8 or 10dB ?

My confusion lies in the fact that to get maximum SNR reading on the receiver, I have to turn the gain to the minimum. I would have thought that with a ~35m cable run, I would need to turn up the gain even a little but looks like not? Why would increasing "gain" reduce SNR? Is it because on adding gain I am also adding noise?

Confused...

 

[scopus]

I am a newbie to the multiswitch territory but I've got a Vision multiswitch with an Inverto quattro LNB. All connected up but I am a bit confused as to what various dB readings mean.

First is max B/A gain. My Ku LNB is connected to the A ports, so I am looking at max gain of 10dB or 8dB depending on which receiver port I am connected to.

In addition there are adjustable "pots" for each of the inputs, which I gather change the "gain", between 0dB and 8 or 10dB ?

My confusion lies in the fact that to get maximum SNR reading on the receiver, I have to turn the gain to the minimum. I would have thought that with a ~35m cable run, I would need to turn up the gain even a little but looks like not? Why would increasing "gain" reduce SNR? Is it because on adding gain I am also adding noise?

Confused...

View attachment 153067

No gain control on my Technisat CJ. So this is just a guess...The Technisat specifies a max 15m run from the LNB to the switch, and then up to 100m for each output port. So you're probably over loading by turning up the gain...

 

[Captain Jack]

It's about 2m from the LNB to the switch and then a 35m run. It's a bit of a faff but does work. Just wanted to know the mechanics behind the gain control.

 

[scopus]

It's about 2m from the LNB to the switch and then a 35m run. It's a bit of a faff but does work. Just wanted to know the mechanics behind the gain control.

I think the gain control is more relevant to bigger cascade systems CJ, where finer tweaking is required to gain the correct equalization over all 4 bands..

 

[PaulR]

On the multiswitches I've had which had these gain controls (not all do) I've just set them to mid way with the mental note that if there's a problem somewhere I'd see what fiddling with them would do. Never had to do that so far...