[TenTec] Re: Orion rf gain and inherent noise

[Gary Hoffman]

Grant...

Same question I posed to Jerry.... does COLD help cut the noise down ?  I
can do cold very easily.

73 de Gary, AA2IZ


----- Original Message ----- 
From: "Grant Youngman" <nq5t at attbi.com>
To: <tentec at contesting.com>
Sent: Sunday, June 08, 2003 12:08 AM
Subject: Re: [TenTec] Re: Orion rf gain and inherent noise


>
>
> > From my point of view, it would seem the receiver should be quieter
> > But, it would seem that listening to the receiver with the
> > antenna off and the rf gain all the way off you would hear the base
> > level of noise in the receiver.  If this level weren't there, would we
> > be able to copy weaker signals better?
>
> I'm not sure what the source of that slight increase in background
> noise level is with the RF gain all the way down.  It sounds to me
> like a gain increase somewhere else in the system.  But internal
> receiver noise such as it is (pretty low) does not appear to be a
> limiting factor, and you wouldn't be looking for weak ones with the
> RF gain backed off anyway.
>
> The "RF" gain doesn't go anywhere near zero.  (I wonder if this is
> really an IF gain block in the DSP).  At the lowest gain setting, a 2
> uV signal is still very audible.
>
> Without doing any rigorous signal to noise measurement, the radio
> hears well below 0.1uV, and, with the preamp on, signals at 0.05uV
> and below are clearly discernable (CW, 1Khz bw).  Your'e never
> going to find a band that quiet in any case.
>
> At the spec points of 0.18uV with the preamp on and 0.5 uV with the
> preamp off, signals are strong, clear and well aboveinternal noise.
>
> I'd just leave the RF gain alone.  You'll hear whatever is out there to
> be heard.
>
> In passing I managed to confirm that the S-meter is set for S-9 with
> right at 100uV at the antenna. (SUB receiver selected to a different
> antenna).
>
> Grant/NQ5T
>
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