[TenTec] UCW and LCW

[Ron]

Sinisa,
Since I first replied to your post, I've worked through this more carefully.
The setup:

BW @ 600 Hz (using a 600 Hz roofing filter)

PBT=0

With this setup, the frequency of an interfering signal is placed higher or
lower in tone when changing from UCW to LCW.  When it is heard as a high
tone in UCW, it is then heard as a low tone in LCW.  When it is no longer
audible in UCW, it is no longer audible in LCW, so the filter symetry would
seem to be good as you say.  The only advantage found in changing from UCW
to LCW is the "mental filter" of rejecting a higher or lower tone.  So my
statement "As a practical matter it seems to completely eliminate some
interfering signals when I change from UCW to LCW", has to rely on the
individual "mental filter" because the signal will remain in the audio ouput
of the ORION II.

As you say, it is best to reduce BW and not rely in UCW / LCW for a filter.

73
Ron KA7U


-----Original Message-----
From: tentec-bounces at contesting.com
[mailto:tentec-bounces at contesting.com]On Behalf Of Sinisa Hristov
Sent: Friday, November 03, 2006 12:35 PM
To: tentec at contesting.com
Subject: Re: [TenTec] UCW and LCW


Ron Morell wrote:

> As a practical matter it seems to completely eliminate some
> interfering signals when I change from UCW to LCW.


Ron, could you, please, try it again,
taking care about following:

  a) exactly the same BW is used on both UCW and LCW
     (BW can be altered by pressing LCW/UCW);

  b) PBT = 0;

  c) the roofing filter used is significantly wider than BW,
     i.e. 1 kHz filter with 400 Hz BW.

Under above conditions there should be no change in inteference level,
no matter what the inteference frequency is. This follows from the
symmetry of filter's response - Orion's DSP filters are very accurately
symmetrical.

Some asymmetry may be introduced by roofing filters,
but nevertheless for interference reduction one should
rely on reducing BW, and not on UCW/LCW switching.


73,

Sinisa  YT1NT, VE3EA


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