[mythtv-users] Hauppauge 1609 and Pixelation Tests

Barry Martin barry3martin at gmail.com
Mon Jun 3 23:12:50 UTC 2019


Hi Stephen!


>>                  --------1600
>> Antenna ---- 4x -----1600
>>                  --------2500
>>                  ----------------------------------1609
>>
>> (If the diagram gets clobbered the antenna feeds to the 4x splitter.?
>> The four tuners feed from the 4x splitter.)
>>
>> '4x' is a 4-way signal splitter.
>>
>> The 1600 and 2250 tuners are inside the old Backend (BE1); the 1609 is
>> inside the new Backend (BE3). The signal strength to the 1609 should be
>> the same as what is going to the 1600 and 2250. What happens inside the
>> tuner card with single, dual and quad tuner devices is another level.
> OK, so each of those cards is getting a little less than one quarter
> of the signal from the aerial.  On the 2250 card, that is then split
> again so that each of its tuners is getting only less than 1/8 of the
> aerial signal.  So those tuners would be the ones most likely to be
> affected by pixellation or total loss of signal when the aerial signal
> is degraded.

    Yes; there is a pole-mounted antenna amplifier to compensate some
    for the signal losses. Had tied without the amp – the 1600 and 2250
    tuners were not happy.. And the pixelation issues I have with the
    old Backend do not appear to have been due to AGC overloading of the
    amp circuitry – two simultaneous recordings on different tuners did
    not cut out concurrently. Also with the way the new Backend with the
    1609 quad-tuner is connected in via the 4x splitter it is getting
    the same signal as the old BE with the old tuners. The old BE can
    have a <pbbt!> recording and the new BE can have no/minimal issues.


> In the 1609, if the speculation is right, there is a low noise
> amplifier (LNA) on its aerial connection, which boosts the level to a
> bit over 4 times the input level, and then feeds a 4 way splitter so
> that each of the 4 tuners gets the same level as the input - a bit
> less than one quarter of the aerial signal.  The LNA and splitter seem
> to be on-silicon, and are likely high quality, with very little loss
> of signal quality compared to the normal sort of aerial amplifier and
> splitter that are available retail for aerial systems.  It is not
> unlikely that the LNA actually adjusts its amplification level to
> match the requirements of the tuners, so that each of the 4 tuners is
> getting an optimum signal level, no matter what the input aerial
> signal level is.  The net result is that all 4 tuners work very well.

    Certainly appears so in my unscientific tests! ...I will have to
    test if the pre-amp is still needed after removing the 4x splitter.




> By the way, people who were used to the old analogue TV usually have
> the wrong idea about pixellation.  They think of it as degraded
> picture, which was a gradual thing in the analogue system, ranging
> from present but not visible except to a trained eye, through nasty
> but still watchable, all the way to completely unwatchable (but the
> audio was usually still hearable).  But in the digital system,
> pixellation is really loss of signal for short periods, not degraded
> signal.

    Yes: half-know the analog signal’s fluctuations and drop outs were
    better tolerated by the human brain as a more natural rise and fall
    as opposed to a digital signal’s square wave rise/fall. The brain
    was able to sort of fill-in the missing/erroneous analog signal. And
    of course the faulty digital data gets displayed as odd-coloured
    squares, again not found in nature. You gave the technical
    explanation, which did fill in some of my ‘pixelated’ learning. <g>



> The difference in signal level between 100% reception and no reception
> at all (no valid packets received) is actually quite small.  And all
> the digital signals have been carefully designed to be resistant to
> the usually problems that plagued analogue signals.  For example,
> analogue ghosting, caused by receiving the same signal via multiple
> different paths and hence at slightly different times, is virtually
> completely eliminated by the way DVB and ATSC signals are broadcast -
> the ghost signal(s) are simply ignored.

    Yes, digital does provide a sharp picture when the Propagation Gods
    allow!


    Thanks again!

    Barry





-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mythtv.org/pipermail/mythtv-users/attachments/20190603/98002624/attachment.html>


More information about the mythtv-users mailing list