On 13 May 2008 19:42:54 GMT Jim Yanik <jyanik@[EMAIL PROTECTED]
> wrote:
| Strongbox <strongbox@[EMAIL PROTECTED]
> wrote in
| news:gxzyklsar3tn.1sis1ac1fdf4x$.dlg@[EMAIL PROTECTED]
|
|> On 11 Mar 2008 17:13:55 GMT, Jim Yanik wrote:
|>
|>> the signal from a splitter is 3 db down from the input signal(OTA
|>> antenna). That can mean the difference between getting a channel and
|>> NOT getting it.
|>
|> Yep. Just add an inline amplifier.
|>
|
| sorry,that adds NOISE,decreases signal/noise ratio.
| On an already weak signal,it does not improve things.
| When the signal is in the "mud",adding an amp raises the level of the
mud
| the same amount as the signal.
|
| (all amplifiers add noise)
This is absolutely correct! An amplifier can never "fix" a signal that is
weaker than the received noise.
However, if the noise figure of the receiver itself is pu****ng the noise
level
above the signal, that would otherwise be sufficient to overcome the
noise,
a low noise pre-amplifier may be able to fix it (if its own level of noise
is
not too high). One should think of this not as amplifing a signal, but
rather
as improving the receiving system noise figure.
Still, it is best to place that preamplifier at the antenna, or as near to
it
as possible, to boost signal to also overcome the feedline losses (in
addition
to any poor noise figure the receiver may have).
Further consideration may need to be given in certain cases to the
directivity
of the antenna and the intermodulation distortion of the preamplifier or
even
the receiver. Too many, or too strong, undesired signals getting into the
amplifier or receiver, can produce intermodulation products that can
interfere
with the desired signal. Notch filters for interferences, or band pass
filters
for the desired signals, may also help in problem cases.
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