[mythtv-users] Strong signal, ugly artifacts...
sarkiaponius at alice.it
Sat Jun 6 08:26:07 UTC 2009
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.
> 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>>>
>> I'm seeing horrible artifacts in my DVB-S recordings, even
>> 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.
> 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.
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