SNR Levels

I appreciate there are a lot of factors governing digital reliability
and I am curious as to certain readings on my BT badged Netgem digital
set top box.

I live in HA88YH and am 16 miles from Crystal Palace transmitter. I
have a loft aerial going in to a Proception variable gain masthead
amp. This is feeding three TVs.

Reception is steady and the only problem I occasionally get is when a
motorbike goes past outside when I get a little pixelation.

Now to my readings.

All 6 multiplexes give about 26SNR and a signal quality of about 82 to
85%.

Is there a SNR minimum or is this just one factor amongs many.

Geoff Lane

In article , Geoff Lane
wrote:
I appreciate there are a lot of factors governing digital reliability
and I am curious as to certain readings on my BT badged Netgem digital
set top box.

I live in HA88YH and am 16 miles from Crystal Palace transmitter. I have
a loft aerial going in to a Proception variable gain masthead amp. This
is feeding three TVs.

Reception is steady and the only problem I occasionally get is when a
motorbike goes past outside when I get a little pixelation.

Now to my readings.

All 6 multiplexes give about 26SNR and a signal quality of about 82 to
85%.

The problem is to determine how these values were estimated by your set top
box. A carrier-to-noise ratio of 26dB is high enough that you should not
get many noise generated errors.

FWIW My Nokia also gives a CNR whose value seems to 'saturate' at about
26dB, and it does not vary linearily with the reported signal level. :-)
However - as with your box - I have no idea how it gets these guessimated
values.

Is there a SNR minimum or is this just one factor amongs many.

As you have found, impulse interference can be problem when it occurs.

If curious, try something like a few of the inline pad attenuators from
Maplin. These will give a guide to how much you can drop the signal before
you encounter serious problems due to noise in the set top box, etc.

Slainte,

Jim

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On Mon, 27 Nov 2006 10:26:46 +0000 (GMT), Jim Lesurf
wrote:


Is there a SNR minimum or is this just one factor amongs many.

As you have found, impulse interference can be problem when it occurs.

If curious, try something like a few of the inline pad attenuators from
Maplin. These will give a guide to how much you can drop the signal before
you encounter serious problems due to noise in the set top box, etc.

Thanks for interesting reply..

Geoff Lane