[mythtv-users] ATSC tuner advice wanted

Stephen Worthington stephen_agent at jsw.gen.nz
Sun Aug 22 04:06:22 UTC 2021

On Sat, 21 Aug 2021 17:10:22 +0000, you wrote:

>None of the consumer based tuners tend to have
>great RF tuner/demods (at least compared to
>your average TV, which tend to have much better
>RF devices).

The most likely cause of tuners appearing to be worse than TVs is that
most tuners these days come in multiples, or are used in multiples. To
get signal to each of the tuners, the incoming signal needs to be
split, so if you have two tuners in a unit and only one aerial
connection feeding it, each tuner will be getting just less than half
the signal that is coming in on the aerial connection.  So a TV with
one aerial connection feeding one tuner will be getting twice as much
signal as each of the dual tuners.  Splitting a signal four ways is
even worse.  I think that it is probably a myth created by this effect
that makes people say that TV tuners are better.  As far as I know,
manufacturers use the same chipsets in tuners and TVs.

Fortunately, a number of the latest tuners seem to have a decent fix
for this problem.  Instead of just using passive splitters, they have
an amplifier/splitter, so each tuner gets fed a signal that is the
same level as the incoming signal.  There will be a slight decrease in
signal quality from passing through the amplifier/splitter, but
because the chips doing this seem to use quality low noise processing,
the degradation is minimal.  This is what my TBS-6909 (8 x DVB-S2) and
TBS-6209 (8 x DVB-T2/DVB-C) PCIe cards do, and the result is
excellent.  I hope that the latest ATSC devices will be using this
technology too.

So when choosing a multi-tuner unit now, you need to be looking for
one that uses a builtin amplifier/splitter.  But it is quite difficult
to tell from the advertising which ones do and which ones do not. Ones
with four or more tuners seem to be likely to be working this way, and
the more modern design the better as the chipsets that have the
amplifier/splitter are relatively new (maybe five years old?).

With manufacturers who do answer questions (SiliconDust?), I would ask
them and see what they say.

If you have multituner devices that do not have an amplifier/splitter
builtin, you will likely need to use your own low noise external
amplifier, and preferably one that has adjustable levels.  These are
typically not the units you can buy retail.  Retail units often use
low quality (higher noise) amplifiers and offer no controls at all.

More information about the mythtv-users mailing list