[mythtvnz] Pixellation Every ~ 20 minutes

[Curtis Walker]

On 14 October 2012 12:22, Paulgir <paulgir at gmail.com> wrote:
> On Sun, 14 Oct 2012 11:11:44 +1300, tortise <tortise at paradise.net.nz> wrote:
>
>> On 14/10/2012 8:11 a.m., Paulgir wrote:
>>
>> FWIW the Hdhomerun's have an android signal meter app available which
>> would likely help tune antennae orientation. Its pretty cool geekware! It
>> may be helpful to watch the signals over the Pix periods.
>>
>> Is there some local signal interference event happening every 20 minutes?
>>
>> It seems to me that the rules and difficulties of analogue signal
>> alignment are not the same for digital signals, others here may be able to
>> clarify better?
>>
> I'm unsure about the 20 to 30 min cycle some of us are seeing.I did see the
> the period become more random after I reduced the signal.
>
> I have just been out playing with the Antenna orientation.I swung the
> antenna 30 degrees either side of the existing aim,with interesting
> results.I could improve the TV3 signal strength and quality by moving away
> from pointing directly at the transmitter at the expense of Prime and
> TVNZ,but still getting acceptable results on those frequencies.The high
> frequency (TV3) is more sensitive to targeting  and pointing directly at the
> transmitter is not optimum for my location.I have left it pointing about 5
> to 10 degrees west of the transmitter.It's not perfect but hopefully testing
> will show some improvement in recordings.
>
> -Paul
>
>
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An update.

1. I rechecked and redid all of my F-connectors (one of them was a
little shoddy). I also redid the balun connection at the aerial.

2. I realigned the aerial to Hamilton infill - yes, with a 91-element
array it's probably overkill, as evidenced by the fact I picked up
"Panasonic Blu-ray" and a couple of technical channels (with no
picture) on mythtv full scan. Signal strength and quality are both
reported as 10/10 for all three muxes on my TV's built-in signal
meter.

3. Doing the above reduced the pixellation to every ~30 minutes, but
it's still there, and still exactly the same type (steadily worse over
a minute, then monet-like with sound glitches before suddenly coming
right after another minute or so).

4. To try to see if too much signal was the problem, I bought a
variable attenuator
(http://www.jaycar.co.nz/productView.asp?ID=LT3050&keywords=attenuator&form=KEYWORD).
At about half-way, the TV's signal meter drops to 9/10 strength.
Quality is still the same (10/10). On myth, am still getting the
pixellation every ~30 minutes.

5. No errors in the log files i.e. no "mythbackend" logs are being generated.

6. I used a script to clean up orphan files (find_orphans.py:
http://www.mythtv.org/wiki/Find_orphans.py, which had been generating
some backend errors. Still not the fix.

7. Am wondering whether FM interference could be a problem, so might
try an FM attenuator/trap if I can find one in NZ
(http://www.antennasdirect.com/store/filter-attenuator.html)

8. Might try a smaller aerial (43 element), although I would have
expected the attenuator to fix the problem if that was it.

9. Will wait a couple more days to see if attenuating the signal
further might help, and will check CPU/RAM/disc useage logs to see if
something is spiking when the recordings go dud.

10. Might try a USB tuner to see if it's the Hauppauge HVR-2210 - any
recommendations for one which works well with linux? There are a bunch
on trademe, but not sure what's a good one.