[mythtv-users] Strong signal, ugly artifacts...

[William]

On 06/04/2009 05:59 PM, Robert McNamara wrote:
>
>
> On Thu, Jun 4, 2009 at 2:53 PM, Andrea Giuliano <sarkiaponius at alice.it 
> <mailto:sarkiaponius at alice.it>> wrote:
>
>
>     Robert McNamara wrote:
>
>
>
>         On Thu, Jun 4, 2009 at 1:51 PM, Andrea Giuliano
>         <sarkiaponius at alice.it <mailto:sarkiaponius at alice.it>
>         <mailto:sarkiaponius at alice.it <mailto:sarkiaponius at alice.it>>>
>         wrote:
>
>            I'm seeing horrible artifacts in my DVB-S recordings, even
>         though
>            MythTV says the signal strength is 99%
>
>
>         Signal strength isn't what you think it is.  Signal strength
>         is the strength of the electrical signal between the card and
>         the LNB, *not* an indication of quality of the signal.  More
>         helpful for this is SNR (Signal to Noise Ratio) and Bit Error.
>          Low SNR or high bit error means bad quality signal.  Repoint
>         the dish.
>
>
>     Dear Robert,
>
>
>     thanks for your kind answer. Can you please give me reference
>     values for SNR and Bit Error? I got 4.8 dB and 2000-3000 for them,
>     depending on the channels. Actually, SNR seems to be constant, I
>     mean it's alway 4.8 dB, while BE changes instead.
>
>
>     Also, my dish works perfectly fine with my stand alone decoder (I
>     have two cables from one dish), so I guess it's not its fault.
>
>
>     Best regards.
>
>
> (Fixed top posting)
>
> Hi Andrea,
>
> Ideally, the BER should be 0 or extremely close to 0.  Different tuner 
> devices have different signal sensitivities and different decoders are 
> more or less sensitive to errors in the stream.  Both are likely 
> problems for you.  You will almost definitely need to point your dish 
> more accurately.  You can also check all your cable termination, the 
> cables themselves, and any power inserters for the LNB.
>
> Robert
>

The issue is your 4.8 dB SNR. This is very weak and means your signal is 
very noisy. A good reading will be 10dB or more. You should be seeing a 
low BER starting at around 6dB however bad weather will cause you to 
have signal drop outs. You need to check antenna pointing, all the 
cables (water getting into the cable will ruin it even if it looks great 
so if you have any outside cable connections that are not waterproofed 
(covered with a boot or wrapped/painted with coax sealant) I would redo 
those connections and check signal strength again.

W.
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