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

[Andrea Giuliano]

Okay, I'll check the dish and the cables, when the wind gets weaker 
(indeed, here the wind is quite strong very often, and it's a miracle 
that the dish has moved just slightly in five years!).

Many thanks to everyone.

William wrote:
> 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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-- 
Andrea