[TenTec] Hearing disabled CW OP Seeks Special Omni Filter

[Paul Gates, KD3JF]

I have grown to like the 800hz tone. That was the tone the FCC used when i got my General license 47 years ago and since then have just got used to it.
 
Paul, KD3JF
Glen Burnie, MD
FM19qd (Map Grid Square)



----- Original Message ----
From: Bill Tippett <btippett at alum.mit.edu>
To: tentec at contesting.com
Sent: Monday, May 1, 2006 9:31:50 AM
Subject: [TenTec] Hearing disabled CW OP Seeks Special Omni Filter


VE1CHS wrote:

>My hearing is 12 db down at about 500 Hz, but as much as 45 db down at the
880 Hz CW note in the Omni VI plus. At 1500 Hz, am as much as 70 dB down.
Have constant ringing tinitus at high frequency due to irreversible damage
in the cochlea.

         Peter, you didn't say what exact pitch
you prefer, but I've also used a very low pitch
to copy weak signals for many years.  My hearing
is excellent at all frequencies (according to
audiogram tests) but for some reason my ears seem
to yield better signal-to-noise when using a low
pitch.  My normal DX setting with Orion is 270 Hz,
but I sometimes go as low as 240 Hz and never
above 450 Hz (I use 400-450 Hz only in contests
when I need to hear off-frequency callers).  One
of the reasons I never considered many rigs made
in the 90's (Omni among them) was the fact that
pitch could not be adjusted lower than 400 Hz.
When the FT-1000MP came out with pitch front-
panel adjustable to 300 Hz (in 50 Hz steps),
I switched to it in 1997 from the TS-930S I had
used since 1984.  300 Hz was still higher than I
preferred but it was "close enough" considering
other MP advantages like digital control, etc.

         If you don't mind changing rigs, you have
two alternatives to the Omni.  My main rig for
many years was the Kenwood TS-930S.  This rig
allows a continuously adjustable low CW pitch
while maintaining IF filter centering using an
analog technique.  Not only is the passband
centered on your desired pitch, but you can also
use Variable Bandwidth Tuning (VBT) to narrow
the passband for whatever filters are installed
in the rig.  The 930 does this by shifting the
2nd and 3rd IF passbands in opposite directions
resulting in a narrower (although worse shape
factor) passband.  You can also choose not to use
VBT for best passband shape factor.  Used 930's
are available for around $500 and I would
recommend dual 500 Hz Kenwood or 400 Hz Inrad
filters for the 8.8 MHz and 455 kHz IF's.  Inrad
is also working on a roofing filter for the
TS-930S which should give it very competitive
IMD performance to rigs like the FT-1000MP, etc.

         If cost is not a consideration, Orion
is another alternative.  You can set pitch as
low as 100 Hz in 10 Hz steps with all IF's
perfectly centered by digital control of the
IF offsets.  Used Orions are now available for
around $2500.  This is the ultimate solution
but it may be more than you want to spend.

         Although the Omni can be made to work
at 400 Hz pitch, I believe the IF passbands are
actually centered higher (500 or 600 Hz?).  It
would be possible to retweak the IF frequencies
to center them on 400 Hz for CW only, but that
would then present problems if you also wanted
to use SSB in the same rig.

                                 73,  Bill  W4ZV



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