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[TenTec] TT vs. INRAD Filters

To: <tentec@contesting.com>
Subject: [TenTec] TT vs. INRAD Filters
From: ac5aa@juno.com (ac5aa@juno.com)
Date: Thu, 17 Jun 1999 21:21:11 -0500
Forget the advice about the Timewave DSP.  It will NOT do what crystal
filters will for you.  It only adds selectivity on the resultant audio. 
I really like DSP (and both the Omni's DSP and my JPS NIR-12), but they
are not the same as IF selectivity and should only be considered after
one has exhausted those options!

        73,  Duane   AC5AA

On Thu, 17 Jun 1999 13:35:44 -1000 "Jim Reid" <jreid@aloha.net> writes:
>
>Gunner wrote:
>
>> You have obviously substituted the TT filter #282 with an INRAD #751 
>in 
>> your OMNI VI+. What changes in CW reception performance did you 
>notice? 
>
>For info,  this substitues for the TT 6 pole 250 Hz BW filter,  
>the INRAD 8 pole 250 Hz filter.
>
>For me,  essentially no difference, but I seldom use the
>250 Hz  bandwidth filters!.  I find the INRAD 400 Hz filter
>in the second IF, 6MHz,  replacing the TT #285 500 Hz filter
>the most useful,  especially when also using the NR
>button for DSP:  this also introduces very noticable and
>useful audio peaking,  a la the Yaesu audio peak "filters".
>
>> Easier tuning? Less ringing? Easier readability? Better DSP noise 
>> suppression?
>
>Don't think so,  but I have not attempted a test in a dense CW
>environment,  such as a contest weekend,  so I really
>shouldn't even try to comment,  hi.  I find S&P tuning to not
>be possible with the 250 Hz filters in line; only occasionaly
>switch to 250 Hz bandwidth.
>
>I am more interested now in learning if the "sound" of my
>Omni VI+  CW note would be improved were I to install
>the INRAD 2.8kHz filter in place of the TT 2.4 in the
>first 9 MHz IF.  Some say it makes a great improvment,
>others seem not to tell a difference. 
>
>Were I to do it again,  I would have stayed with the stock
>TT 250 Hz filter, 6MHz IF.  Using the INRAD 753 400 Hz filter
>in the 9 MHz IF,  cascaded with the INRAD #700
>8 pole 400 Hz filter in the 6.3 MHz IF seems to provide
>plenty and sufficient selectivity for me,  especially with
>the TT NR DSP engaged.
>
>Note also,  that the TT #221 250 Hz filter for the 9 MHz IF
>has much more noticable insertion loss than any of the
>others.  Now maybe,  when it was installed for me as an
>option at the TT factory,  someone forgot to put the filter
>jumper into a higher gain position.  One of these days,
>when next into the rig,  if I should decide to go for one or
>the other of the new INRAD offerings for the "permanent"
>first IF filter (i.e.,  either the new 10 pole 2.4 or the
>2.8),  then I will have a look at the gain jumper for the
>TT #221.  BTW,  this is the 250 HZ filter optimized for
>a 500 Hz CW sidetone selection.
>
>I have recieved one email from a fellow who has placed 
>the INRAD 2.8 kHz filters into both IF chains,  but has
>done so for improved SSB audio,  not to deal with
>reported CW note improvment.  Have also heard
>from a fellow who has put the new INRAD 10 pole
>2.4kHz filter in the first IF, 9Mhz,  and is absolutely
>delighted with the improved SSB selectivity from the
>steeper skirts of the new INRAD filter.
>
>Of course,  you cannot add the 2.8Khz filter for
>improved CW note,  and the new 10 pole 2.4kHz
>filter in the same rig:  they both go into the same
>socket in the Omni VI.  That is the permanent first
>socket that is "in" the firtst IF path all the time,  and
>not switched in/out via a button push.  You must
>decide if you want to improve your SSB selectivity
>capabiltiy,  or how you sound on CW!
>
>And,  finally,  have an email suggesting that I should
>forget these IF chain crystal filters,  and instead,
>buy the Timewave DSP-599zx device to achieve
>"brick wall" selectivity in both the CW and SSB audio 
>spectrum.  Of course it is priced at nearly the cost
>of four IF crystal filters when I consider air shipment
>out here to Kauai,  hi.
>
>
>73,  Jim,  KH7M
>
>
>
>--
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>

Duane A. Calvin, AC5AA
Austin, Texas
ac5aa@juno.com -or- ac5aa@earthlink.net
Day:  dacalvin@us.ibm.com

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