[TenTec] Quietness/Apparent Sensitivity

[Duane Grotophorst]

--- Jim Reid <jimr.reid at verizon.net> wrote:
> >From my few hours with my new Orion,  I believe
> what the
> Orion is doing is "suppressing" the noise some 20 to
> 30 dB
> lower than any of us have ever expericenced befoe!! 

Perhaps a better way to express this is to say that
the Orion does not ADD as much noise as other
receivers do. It is a common misnomer when folks say
that a receiver "pulls" a signal in, or out of the
noise. They do neither; instead they can only seek to
preserve the signal to noise ratio of the signal that
enters the antenna connector to begin with; - and to
then make it understandable at an audio frequency (or
decodable for advanced digital modes).

Another widely misunderstood concept is gain vs.
sensitivity in a radio. Most JA radios have plenty of
overall gain, but when it comes to hearing a signal at
or below the noise level they are not necessarily any
better. There's nothing that my IC-765, 706, 820H can
hear that the Pegs (with DEM transverters for V/UHF)
cannot. The Icoms can put more sound to the speaker
but it is both noise and the signal, the desired
signal itself is not any higher above the noise at
all. And the Pegs are just midrange in terms of LO
phase noise. They do however have very quiet IF and
audio chains.

  The
> Orion typ. phase noise spec is just amazing,  -136
> dB/Hz,
> or some such.  Makes a huge difference when
> comparing my RX-340 and the Orion;  the Orion is
> dramatically more quiet,  or weaker signals really
> stand out.  Why?  The noise is much farther down.

This would be consistent with the declared specs for
the LO phase noise for each of those radios. There are
probably a number of other design features in the
Orion that also limit the amount of added noise. 

Duane
N9DG


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