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[sevenlayermuddle]

Apologies in advance for the long post, I'm wondering if any of you kind folks can help me to understand a spec.  for a distribution amp ( Philex SLx8) ?

The device is an 8-way splitter, with a 9th output (the 'Full' output) which is described here: http://technical.philex.com/downloads/rf/SLx8.pdf
as

a signal of the same strength as your aerial downlead

...I believe it's basically provided so that you can cascade a second distribution amplifier if you need more than 8 outputs.  The thing is, the data sheet here:  http://technical.philex.com/downloads/rf/SLX.pdf lists the "Full Output" as having a gain of 18dB.  Eh?  How can it have a gain of 18dB and yet still be the same strength?   I'm wondering if the '18dB gain' refers to equivalent amplification after the losses incurred by passive splitting, which would make more sense, so the 'Full' output is only a few dB higher than the input.

My follow on question is that the individual outputs specify a gain of 8dB.  Does that also refer to the gain after splitting losses, in which case is there may actually be a 'net loss' on these individual outputs, compared to the signal from the aerial downlead?

To put these numbers in context I've seen it quoted that the loss of a two-way split is usually about 4dB, so the result of an 8-way split would be a 12dB loss.  By the above interpretation, that would suggest the 'Full' output was actually +6dB net, while the individual outputs were each -4dB net.

edit: PS:  I'm not expecting anybody to go off and read these .pdfs that I linked.  I just provided the links out of good manners to show the source of the quoted material 

[HPsauce]

Hmm confusing and inconsistent documents I'd say.

I happen to have one of that exact model in my loft and I think the data sheet is correct.
Why? Because I use that "full" output and it feeds (at some distance) a passive splitter that then goes to 2 different TV's which both work fine.
I'm watching one of them as I type this - the Freeview TV tuner in my PC.
I'm pretty convinced that the "full" output is significantly higher power than the other 8.

PS This is used with a masthead amplifier (on TV) and both TV and VHF aerials fed in.

[sevenlayermuddle]

Hmm confusing and inconsistent documents I'd say.

I happen to have one of that exact model in my loft and I think the data sheet is correct.
Why? Because I use that "full" output and it feeds (at some distance) a passive splitter that then goes to 2 different TV's which both work fine.
I'm watching one of them as I type this - the Freeview TV tuner in my PC.
I'm pretty convinced that the "full" output is significantly higher power than the other 8.

PS This is used with a masthead amplifier (on TV) and both TV and VHF aerials fed in.

Thanks HP,

It seems we have a lot in common as my goal (as yet unstated) is to get a signal that's strong enough to satisfy a PC freeview card.  I'm not sure if the card is just greedy for volts, or the inside of the PC case is just too hostile, but it does seem to need a strong signal and I'm thinking about using the 'full' output to see if it improves matters.   My card is a 'dual tuner', which probably means there's a splitter just inside which won't be helping either.   It's reassuring to hear that something similar worked for you, I'll be in  the loft trying it tomorrow.

I'm still not clear though, even accepting that the 'full' output is clearly stronger than the other outputs, where they (all) stand relative to the input signal?

- 7LM

[HPsauce]

I've got a Hauppauge Freeview only PCI card, can't remember the model name on the box (something like Nova-T?) but Device manager shows it as a WinTV 88x DVB-T.
My experience is that it actually gets better reception than most of the TV's/PVR's/digiboxes that we have.

PC it runs in is a lowly Celeron 2.6GHz so it uses a fair proportion of the CPU (typically 30%) and that figure is very sensitive to driver versions and some technical settings. I've twiddled it over the years and am now leaving it alone as the PC will soon be replaced by something far faster.

[sevenlayermuddle]

I've got a Hauppauge Freeview only PCI card

snap!

Thereafter the comparison breaks down as mine's in a box which just serves as a (linux) mythtv backend, so the  it's the frontends (one MAC, one Linux)  that have to do all the graphics work.  All the host PC has to do is stream data to disk and to LAN at a rate of 2-3mbps, hardly much of a challenge these days.

Still, it's worrying to hear yours gets better reception than your TVs.  My TVs, PVRs etc are all 100% fine, it's just the hauppauge that grumbles about signal levels, and keeps pixelating.  Maybe mine's just a dud, and I could have sent it back,  in which case I'll regret having already tried to 'improve' the solder-work around the aerial socket, who's grounding wasn't very convincing.  Dear oh dear   

- 7LM

[roseway]

Which model of Hauppauge card do you have? I use a Nova-T 500 dual-tuner card in a Linux system, and I find the same as HPSauce, that its reception is rather better than my Freeview PVR and my TV set. I live in a weak signal area and use a distribution amplifier. When I was originally setting this up I did notice that Freeview performance varied widely between different amplifiers.

[sevenlayermuddle]

Mine's called a Nova TD-500.  The 'D' is for the optional (windows-only) diversity mode, whereby it has a second aerial input and both tuners join forces to give the best signal on a single channel.  When not used in 'D' mode, you just use the top socket,  the second one seems be pretty much open-circuit and (I've tried) contributes no signal.

The 'D' was all I could find at the time and, before I bought it I did much googling, and found conflicting answers about whether or not it was similar to a T-500, and whether or not it would work in bog-standard Linux.  Apart from sensitivity however, it actually worked a treat, straight out of the box.  There's supposed to be option for the T-500 to enable a 'low noise amplifier', but it seems to have zero effect with the 'D', there seems to be general agreement on that in the forums.

The circumstances in which mine struggles the most is when both tuners are on the same multiplex, at which point occasional pixelisation becomes continuous.  I imagine that each tuner has a tuned circuit that resonates its load at the frequency being received, and when both tuners are loading the same frequency at the same time, there's just not enough signal to keep them both happy