[mythtv-users] Help setting up HD Homerun
MythTV_01 at appropriate-tech.net
Thu Nov 20 21:00:34 UTC 2008
At 10:39 AM 11/20/08 -0800, David Brodbeck wrote:
> Keep in mind that preamps are widely misunderstood. They're mainly
> useful for overcoming cable and splitter losses between the antenna and
> the receiver. If the signal you're trying to receive is weak, down
> close to the noise floor, the amp won't help -- in fact it will just
> make it worse, because an amplifier will always degrade the
> signal-to-noise ratio. The only remedy for a poor signal-to-noise ratio
> is a more directional antenna.
Exactly so, but let me clarify something...
In most cases (i.e., let's not get bogged down with side issues like
multipath, etc.), the "cure" to that S/N problem is not actually more
directionality, per se; it's more native *gain* (over isotropic) in the
antenna -- i.e., simply a stronger signal being shoved down the wire.
While it is strictly correct to equate total antenna gain with total
directivity, this only holds true when we look at the polar response
patterns in *both* the horizontal and vertical planes. Yet the latter
nearly never really matters in practice, unless you're dealing with very
hilly terrain or trying to shoot over the horizon on a ground reflection.
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