[mythtv-users] Coax splitters - how painful are they?

Brian Wood beww at beww.org
Tue Sep 25 14:01:41 UTC 2007

Dan Ritter wrote:
> On Tue, Sep 25, 2007 at 03:29:31PM +1000, William Pettersson wrote:
>> should have decent signal, I pick up analog SBS pretty much perfectly.
>> Anyway, I now want to upgrade my system, more hard drive space and
>> another tuner.  Actually another two tuners would be nice I reckon.
>> Is it possible to get decent coax splitters that don't have too much
>> signal loss?  Is it worth me trying to hook up a splitter for my third
>> tuner, if I only plan to use it once or twice a week, or should I just
>> grab a dual tuner, and be forced to skip the occasional program here and
>> there?
> For two tuners, I would use a passive splitter; for four tuners,
> I would consider a four-way powered splitter. But if your signal
> strength is exceptional -- as yours may be -- even a 4-way
> unpowered splitter may work.

You want to have at least 0dbmv. on each channel going into the tuner,
and no more than +10dbmv.

A "perfect" two-way splitter would have 3db. loss. Since nothing is
perfect in this world, most splitters actually lose 3.5db. per leg for a
two-way split, and 7db. for a four-way.

So, in order to know if you really wanted a powered splitter (just an
amplifier and a splitter in one case) you would have to know what your
levels are.

Also, any amplifier will add noise and third-order products, they should
be avoided if at all possible.

Not that a dual tuner has to have a splitting device in it to feed both
tuners, so you are really asking whether it is better to have the
splitter inside or outside your computer case. Since the splitter on the
dual-tuner card was probably chosen to be as small and cheap as
possible, it's probably better to use an external split.

(I think some dual-tuner cards have what they call an LNA (low-noise
amplifier) to make up the split loss, I suspect that the term
"low-noise" is used pretty loosely in this case, a true LNA would cost
more than the card.


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