Well said, Duane. To put it yet another way, the purpose of the 9 mhz
filters is to reduce or eliminate DSP overload caused by very strong
adjacent channel signals not in the DSP passband.
Carl Moreschi N4PY
----- Original Message -----
From: "Duane Grotophorst" <n9dg@yahoo.com>
To: <tentec@contesting.com>
Sent: Friday, March 07, 2003 2:59 PM
Subject: Re: [TenTec] Orion 9 MHz filters
>
> Or to put it another way they are at the beginning of
> the IF chain, not distributed throughout or just
> before the detector stage.
>
> The purpose and function of the crystal filters in the
> Orion are somewhat different than its non DSP-IF
> predecessors. They are not intended to establish the
> final IF selectivity at all, but are instead intended
> to limit the amount of signal spectrum energy (which
> also includes both unwanted signals and broadband
> noise) that reach the later mixer stages and A to D /
> DSP stages.
>
> As such I would not get too wrapped up now trying to
> decide which additional filter to add (if any) until
> you have put the Orion through it paces for awhile. If
> you do a lot of CW work with strong signals less than
> few hundred Hz away then one of the narrower filters
> may help you, if not they will add little value. Also
> remember that all of the other DSP IF amateur radios
> out there (that I know of) have 15-20 KHz filters
> which are equivalent in purpose to the 9MHz filters in
> the Orion.
>
> I would also be cautious of any third party filters
> that may be prone to ringing, they could conceivably
> hurt RX performance because the DSP IF stage will have
> to deal with both the existing desired signal + noise
> and the filter "added" ringing signal. So for the 9MHz
> filtering in the Orion I would lean toward not buying
> any optional 9MHz filters to begin with, but instead
> wait and see how well it plays without them first, and
> then decide.
>
> Duane
> N9DG
>
> --- N4PY <n4py@qvssoftware.com> wrote:
> > The Orion Crystal filters are roofing filters and
> > not IF filters. The PBT
> > will adjust the DSP IF filters. The DSP filters
> > will lie entirely inside
> > the roofing filter passband.
> >
> >
> > Carl Moreschi N4PY
> >
> > ----- Original Message -----
> > From: "Mark Erbaugh" <mark@microenh.com>
> > To: <tentec@contesting.com>
> > Sent: Friday, March 07, 2003 12:47 PM
> > Subject: [TenTec] Orion 9 MHz filters
> >
> >
> > > As I was replying to someone about the 9 MHz
> > filters in the Orion, a
> > > question occured. On the Omni V and VI, the 9 MHz
> > filters are not
> > tuneable.
> > > The passband is fixed. Only the 6.4 MHz filters
> > are tunable via the PBT
> > > control. Are / will the 9 MHz filters in the Orion
> > have a PBT adjustment?
> > >
> > > 73,
> > > Mark
>
>
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