[TenTec] TT vs. INRAD Filters

[Jim Reid]

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



--
FAQ on WWW:               http://www.contesting.com/tentecfaq.htm
Submissions:              tentec@contesting.com
Administrative requests:  tentec-REQUEST@contesting.com
Problems:                 owner-tentec@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm