DVB: Signal Quality vs. Signal Strength?

[ziphnor]

Hi,

I am using a two-way splitter to split the digital cable tv signal into my 2 DVB-C tuners. When looking the TS capture program available for the tuners i noticed that the signal strength is high, but that the signal quality various greatly, jumping from ~25% to 98%. At the same time i have had some problems with the occasional stutter in recordings and live tv and i was wondering whether or not this could be caused by low signal quality.

Could someone explain to me what exactly signal quality stands for, and similar for signal strength, as well as possibly provide some idea of what the values should be?

[Taipan]

Hi ziphnor,

Signal Strength gives an indication of the relative level (voltage) of the signal and is usually expressed in db. Signal Quality is a measure of the bit error rate (BER) and a poor, or fluctuating, SQ will certainly produce "stutters" in the viewed image.

It is quite possible to have a good Signal Strength reading (~20db), but still get stutters, because the Signal Quality is poor.
The Signal Quality can be poor (< 80%) if there is a lot of EMR interference mixed with the TV signal. This interference can be caused by other electrical devices nearby (some people have suggested that their wireless LAN card causes interference), or by insufficient shielding of the TV signal from the antenna to the TV receiver. This is why quad-shielded cable, top quality shielded splitters and screw connectors are specified for a digital TV aerial installation.

If your Signal Strength is OK (clear, snow-free signal on analogue) and you are getting stutters, I would recommend that you upgrade the whole aerial installation to digital standard. Or find the source of the EMR interference and eliminate it.... :?

HTH...

[ziphnor]

Originally Posted by Taipan

If your Signal Strength is OK (clear, snow-free signal on analogue) and you are getting stutters, I would recommend that you upgrade the whole aerial installation to digital standard. Or find the source of the EMR interference and eliminate it.... :?

I dont know if i would call my analogue signal snow free, i had problems on some channels with diagonal banding, and the digital image quality is definetly much better than the analogue one. Anyway i cant test analogue, because all my cables are now fitted with the connector for digital TV

I think the cabling into my apartment is up to scratch, i was just wondering whether or not the splitter could be the cause of the fluctating signal quality(its a splitter meant for digital cable TV). I guess i should try the signal quality directly, its just a complete mess unscrewing those digital signal cables.

[Taipan]

Originally Posted by ziphnor

i had problems on some channels with diagonal banding,.

Diagonal banding is an indicator of interferrence, so this could also be a cause of your fluctuating Signal Quality, and thus the stuttering.... :?

Originally Posted by ziphnor

I guess i should try the signal quality directly

Yes, that would be a good way to determmine if your splitter is the cause. But, I doubt that it is, unless it has a poor, or broken, connection inside it?

It sounds to me like the problem is the overall quality of the signal back at the antenna - you need to get that as good as possible, first.