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

To: <tentec@contesting.com>
Subject: [TenTec] Re: 2.4khz 9mhz pri INRAD Filters
From: paulc@mediaone.net (Paul Christensen)
Date: Mon, 28 Dec 1998 21:09:41 -0500

Can you elaborate on your BFO mods and what values/part types you used to
improve temperature stability?  At one time I had considered replacing the
majority of BFO trimmer caps with subminiature ceramic NP0 types.

-Paul, W9AC

-----Original Message-----
From: Bill Cook <wdcook@ibm.net>
To: Paul Christensen <paulc@mediaone.net>
Cc: Greg Hodsdon <k7kj@teleport.com>; tentec@contesting.com
To: <tentec@contesting.com>
Date: Monday, December 28, 1998 7:02 PM
Subject: Re: [TenTec] Re: 2.4khz 9mhz pri INRAD Filters

>Paul Christensen wrote:
>> Clarification:
>> I realized that Bill's message was not transceiver-specific.  My
>> 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
>> centered at 9,001.500 kHz  is designed with a lower filter knee of
>> 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
>freq will be less than plus or minus 25hz.  These filters are WIDTH spec'd
>-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
>filter.  I think they "match-up" with the existing circuitry better than
>stock filters.   I would be surprised if TT is paying over $25US for the
>Don't forget that the accuracy of the "BFO" is a major part of this
>After many  tedious hours of parts substitution and tweaking I have finally
>my room temperature
>( 70 deg +/-10deg/f) BFO stability down to plus or minus 5hz.  I do leave
>OMNI VI (ug3) on all the time.  I asked TT if they would make the ARRL Omni
>BFO oven mod generally available; their response was that this was only a
>time deal. Oh well...
>73  Bill Cook   N4WC

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