[TenTec] Hearing disabled CW OP Seeks Special Omni Filter

[Chuck Guenther]

Peter, VE1CHS, wrote: 

Several years ago, perhaps 1998, there was available a special CW filter
(I'm not sure whether at 250 or 500 Hz bandwidth) possibly sold under the
auspices of N4PY to lower the CW note in the Omni rigs.

1) Any chance a list member has one for sale?  Any chance list members know
where I might get one at this late date?

2)  Would also like recommendations/advice regarding exactly what filters I
should buy to get most noise reduction and best performance from the Omni
VI+ on CW.  For example, should I buy 250 or 500 Hz filters for both the 6.3
and 9 mHz IFs? Is the 600 Hz roofing filter available from Inrad
recommended?

http://www.qth.com/inrad/kits.htm#tentec

Is it possible I would actually be happier with 500 Hz filters in the 6.3
and 9 mHz IFs, since one op said they work a little better with the pass
band tuning on the Omni VI+ than the 250 Hz filters do?

3)  If I were able to find the special N4PY "lowered tone" CW filter, what
other set of CW filters should I buy that are compatible with it?

4)  In addition to crystal filters, should I invest in the Timewave
DSP-599zx especially for SSB summertime noise reduction? (As you probably
know, for hearing disabled, getting rid of as much background noise as
possible is a priority for both CW and SSB.)

http://www.timewave.com/dsp599zx.html

Generally, my major interest is CW, but I've got to have good SSB
performance (in the midst of summer QRN) for possible fire emergency work
with the Red Cross this summer."

Hi, Peter

For low-pitch CW work, you want to open up the receiver as much as possible at the low end.  I'd recommend the Omni VI audio mod kit offered by INRAD; also I'd recommend replacing the 2.4KHz SSB filter in the 9 MHz IF chain to an INRAD 2.8 KHz filter. (check the archives on this reflector, though, as you may need to realign the carrier balance).  

The filter you are looking for is the Ten Tec 221 filter (9 MHz IF filter, 250 Hz bandwidth, and offset for a nominal 500 Hz pitch). These are now pretty scarce, except as used items sold occasionally on this reflector.  However, an excellent second choice is the INRAD 753 (9MHz IF, 400 Hz bandwidth, with a 600 Hz offset).  This has quite a bit less insertion loss than the narrower Ten Tec filter-- you may actually prefer it.  

By performing the audio mods and changing filters as described above, you should be able to crank the pitch control all the way down to 400 Hz with satisfactory results.  I've done all these mods on my Omni 6/Opt. 1, and am pleased.  I also have installed the 500 Hz pitch version of the INRAD CW roofing filter.  I never have my pitch control higher than 500 Hz now.  

The 6.3 MHz IF filters are less critical, since they can be centered as desired with the passband tuning control.  I use INRAD 400 Hz and 250 Hz filters in the 6.3 MHz IF.  It is true that the passband tuning control adjustment is pretty fussy with the 250 Hz filter.  

For additional audio filtering and noise reduction, Ive had very satisfactory results with the MFJ-784B tunable DSP filter.  It really helps, even with all the crystal filtering and NR function of the Omni 6.  

73,
Chuck  NI0C