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[TenTec] Re: 2.4khz 9mhz pri INRAD Filters

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Subject: [TenTec] Re: 2.4khz 9mhz pri INRAD Filters
From: wdcook@ibm.net (Bill Cook)
Date: Mon, 28 Dec 1998 19:58:34 -0500

Paul Christensen wrote:

> Clarification:
> I realized that Bill's message was not transceiver-specific.  My preceding
> message applies only to the Omni Six/Six Plus, not previous OMNIs whose
> filters may be compatible in the 9 MHz I.F. stage, including the OMNI V.
> The reason for my concern with the OMNI Six series is that a 2.4 kHz filter
> centered at 9,001.500 kHz  is designed with a lower filter knee of 9,000.300
> kHz, leaving only 100 Hz of error for adequate passband of the CW BFO
> frequency.  As long as the 10-pole filter is precise with predicable QC,
> this filter should still work with the Omni Six/Six Plus.
> -Paul, W9AC


Thank you for your concern.  My experience with the INRAD filter is the center
freq will be less than plus or minus 25hz.  These filters are WIDTH spec'd at
-0hz +100hz;  typically they will fall in the +50hz  range.  Passband ripple is
typically less than 1db.  Another thing, they just work better than the stock
filter.  I think they "match-up" with the existing circuitry better than the
stock filters.   I would be surprised if TT is paying over $25US for the stock

Don't forget that the accuracy of the "BFO" is a major part of this equation.
After many  tedious hours of parts substitution and tweaking I have finally got
my room temperature
( 70 deg +/-10deg/f) BFO stability down to plus or minus 5hz.  I do leave my
OMNI VI (ug3) on all the time.  I asked TT if they would make the ARRL Omni VI
BFO oven mod generally available; their response was that this was only a one
time deal. Oh well...

73  Bill Cook   N4WC

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