Guess I don't understand what up conversion
has to do with the problem.
----- Original Message -----
From: "Duane Grotophorst" <n9dg@yahoo.com>
To: <tentec@contesting.com>
Sent: Wednesday, December 24, 2003 16:45
Subject: Re: [TenTec] Jupiter Extended Report
>
> --- Ben K8DIT <benk8dit@serv.net> wrote:
> > Not there. We are lead to believe that the swept BDR
> > and IMD are half that
> > of the Main Rx on the Orion! There must be a 'rest
> > of the story' there.
>
> Yes there is, the
> Pegasus/Jupiter/RX320/RX350/516/Orion sub RX all
> suffer the same malady as all other radio designs do
> that use up conversion and wide roofing filters do.
> That is they are prone to less that stellar BDR specs
> within the bandwidth of the first IF roofing filter.
>
> > I have both the Omni 6+ and the Jupiter and have to
> > think that there's more
> > going on with the Jupiter than what is being
> > reported.
> > Also, there is a move by some to increase the IF
> > gain by turning an internal
> > pot in the Jupiter. This cant be a good thing for
> > BDR and IMD readings but
> > noone is postulating on its negative potential. In
> > an analog reciver, if you
> > indiscriminately raise the IF gain, results will
> > result in more noise w/o
> > benefit to s/n ration. Is this the case with
> > digitally capable IFs?
>
> Yes there is a down side, the strong signal handling
> capability does degrade, and is in fact quite
> dramatic. The good news is that with proper setting of
> the RF gain control the negatives can be managed. On
> HF the Pegasus/Jupiter do not have any problems with
> S/N ratio, they are very sensitive. Arguably though
> they may be a bit shy for overall gain for the higher
> HF bands. So tweaking IF gain pot will improve the
> overall gain but does makes it easier to overload the
> D to A stage and generate distortion products.
>
> I experimented with the IF gain pot in the Pegasus
> (Jupiter is identical) last January and here's a
> thread that discusses what I found.
>
> http://lists.contesting.com/archives/html/TenTec/2003-01/msg00641.html
>
> Duane
> N9DG
>
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