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On 06/04/2009 05:59 PM, Robert McNamara wrote:
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cite="mid:1aaba6e90906041459o5251498bm78595b352f6cba9f@mail.gmail.com"
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<div class="gmail_quote">On Thu, Jun 4, 2009 at 2:53 PM, Andrea
Giuliano <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:sarkiaponius@alice.it">sarkiaponius@alice.it</a>></span>
wrote:<br>
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Robert McNamara wrote:<br>
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<div class="h5"><br>
<br>
On Thu, Jun 4, 2009 at 1:51 PM, Andrea Giuliano <<a
moz-do-not-send="true" href="mailto:sarkiaponius@alice.it"
target="_blank">sarkiaponius@alice.it</a> <mailto:<a
moz-do-not-send="true" href="mailto:sarkiaponius@alice.it"
target="_blank">sarkiaponius@alice.it</a>>> wrote:<br>
<br>
I'm seeing horrible artifacts in my DVB-S recordings, even though<br>
MythTV says the signal strength is 99%<br>
<br>
<br>
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.<br>
<br>
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<div class="h5"><br>
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<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Dear
Robert,</blockquote>
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<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">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.</blockquote>
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<br>
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<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">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.</blockquote>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;"><br>
</blockquote>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Best
regards.</blockquote>
<div><br>
</div>
<div>(Fixed top posting) </div>
<div><br>
</div>
<div>Hi Andrea,</div>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>Robert</div>
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</blockquote>
<br>
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.<br>
<br>
W.<br>
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