[TenTec] Orion 9 MHz filters

[Duane Grotophorst]

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 at 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 at microenh.com>
> To: <tentec at 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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