[mythtv-users] Network tuners vs. USB Tuners

[James Abernathy]

On Mon, Nov 15, 2021 at 11:42 AM Stephen Worthington <
stephen_agent at jsw.gen.nz> wrote:

> On Mon, 15 Nov 2021 10:14:37 -0500, you wrote:
>
> >On Mon, Nov 15, 2021 at 9:14 AM Barry Martin <barry3martin at gmail.com>
> wrote:
> >
> >>
> >> Hi Jim!
> >>
> >> I have a production remote backend with a Hauppauge WinTV-quadHD PCIe
> card
> >> tuner.  I'm very pleased with it. I also have a test FE/BE combo built
> with
> >> a NUC and it uses a HDHomeRun Connect Quatro.  Both tuners are
> connected to
> >> the same attic antenna via a splitter.  I'm so close to the TV broadcast
> >> towers that I usually get between 90 and 100% signal strength.
> >>
> >> I agree with Stephen Worthington’s comments: too much signal is about as
> >> bad as too little signal and a 2-way splitter might might be sufficient
> –
> >> you might need more! At least you should be able to see if the drop-outs
> >> are lessened. I would suggest rather than leaving the unused terminal
> empty
> >> to add a 75-ohm terminating resistor: with analog signals and
> unterminated
> >> port caused a ‘ringing’ and I presume the same issue with digital
> signals.
> >>
> https://www.amazon.com/outstanding-Terminator-Adapters-Connectors-Satellite/dp/B07V3JBW3L/
> >> (Good Lord! almost $2 each??!!)
> >>
> >>
> >> You might be better with a proper attenuator:
> >>
> https://www.amazon.com/Skywalker-Signature-Signal-Attentuator-16dB/dp/B01MDV701F/
> >> This particular one is 16dB which is probably too much. What I did a
> while
> >> back was get a set of 3 db, 6db, 10 db (etc.; I don’t recall where I
> >> purchased). You can put in series, so a 10dB + 3 dB creates a 13 dB
> >> attenuator. I also have an old switch box attenuator which would be
> handy
> >> for testing other than the contacts have oxidized – need to clean some
> >> day.  Start with the 3dB (which is about the same as the 2-way
> splitter).
> >>
> >>
> >> Personally here I found the Hauppauge 1609 (the quad tuner I think
> you’re
> >> talking about) ‘reacted’ better that the old 1600 and 2250 I had (though
> >> two different systems so other variables) to signal fluctuations; no
> >> experience with a USB quad tuner.
> >>
> >> Barry
> >>
> >
> >Thanks, I do have the 1609 model of the WinTV-quadHD PCIe card. I have not
> >found that it ever has an issue with too much signal. In this case it was
> >the HDHR Quatro that had the pixelation and I think that tuner can be
> >overloaded easily.
> >
> >My house is new enough that it has a data closet where every coax or
> >cat5e/6 cable is terminated.  So my Clearstream 4Max is directly wired to
> >an 8-way splitter in my data closet. There are only a few unused ports and
> >they all have 75ohm terminators on them.
> >
> >As I mentioned previously, I think this may be multipath distortion.
> >Pointing the antenna toward the PBS station 55 miles away puts me aiming
> at
> >neighboring houses and 45 degrees off the direction to the main towers 10
> >miles away.
> >
> >These types of issues come and go with the seasons. Foliage on the trees
> >can impact it as well.
> >
> >I got an A in antenna theory back in college, but should have paid more
> >attention. :-)
> >
> >Jim A
>
> Multipath distortion is a thing with analogue TV, not digital.  DVB
> and ATSC are very well protected against multipath distortion (aka
> "ghosts" in analogue days).  The phase difference caused by the
> different path lengths is seen by the DVB/ATSC receiver and it phase
> locks itself to the better signal.  The reflected signal is completely
> rejected.  So multipath distortion will only cause problems if you
> have reflections that have exactly the same time of arrival.  Since
> the reflected signals always take a longer path than the direct
> signal, they can not cause problems if you are receiving the direct
> signal as well.  If, for some strange reason, you are only receiving a
> reflected signal, then you could possibly get another reflected signal
> with the same path length, but it has to be pretty exactly the same -
> the system detects very small phase differences.
>

I'm no expert but in my research about the upgrade to ATSC 3.0 I've found
that one of the improvements is in the area of Multipath distortion.
Here's a quote from one reference.

"ATSC 3.0 uses Orthogonal Frequency Division Multiplex (OFDM) modulation as
opposed to the 8VSB modulation used by ATSC 1.0. We won’t get too far into
the weeds with that. We’ll just say that OFDM has the reputation of being
more spectrally efficient and less susceptible to multi-path interference
(which can cause ATSC 1.0 signals break up, or not be received at all). "

https://www.nexttv.com/news/atsc-30-everything-you-need-to-know-broadcast-nextgen-tv

Jim A
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