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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