To determine if the INRAD 2.8 kHz filter will be of benefit to you before
committing to a purchase, you may want to try the following test:
Critically listen to your transmitted CW on an alternate receiver using a
relatively wide I.F. and audio bandwidth. While listening to your
transmitted signal on the external receiver send a string of dits and dahs
while alternating between the CW and FSK modes. If the FSK mode sounds
noticably better than CW mode, the 2.8 kHz @ 9 MHz INRAD filter will help.
Functionally and electrically, the only difference in the keyed waveform
between CW and FSK is that the FSK BFO frequency is shifted up, well above
then knee of the stock 2.4 kHz filter. All other key shaping and timing
parameters are identical between the two modes.
-Paul, W9AC
----- Original Message -----
From: "Paul Christensen" <paulc@mediaone.net>
To: <DK2GZ@aol.com>; <tentec@contesting.com>
Sent: Monday, April 30, 2001 8:58 AM
Subject: Re: [TenTec] Chirpy CW-sound on an OMNI 6+
>
> Harry,
>
> You may want to search the Ten-Tec archives for a complete discussion of
> causation and remedies. In my particular case, I was able to improve the
> sound of the keying by taking the following steps:
>
> 1) Changed the CW BFO crystal on 9 MHz Oscillator Board. As I recall,
> keying is accomplished a bit differently between the older Omni Six and
> Omni Six Plus. The amount of crystal shift is less with the Omni Six
Plus,
> but curiously, the new generation Omni Six Pluses seem to manifest the
weak
> CW note more prominently. In any event, I upgraded the circuit board and
> ordered several 9 MHz JAN crystals...about ten in all, each with a
different
> load capacitance value. I then hand-picked the value which had the best
CW
> note.
>
> 2) The CW BFO is fixed a value that is on the skirt of the 2.4 kHz filter.
> This filter is used for both transmit and receive while in SSB and CW
modes.
> The combination of a weak 9 MHz crystal and a transmit BFO frequency
square
> on the filter skirt is what the cause the intensifies the effect of the
weak
> crystal. INRAD now makes 2.8 kHz filters for the 9 MHz IF which extends
the
> filter skirt out of harm's way. This effect is not evident on other
> Ten-Tecs which use higher CW BFO frequencies that fall well within the 2.4
> kHz filter skirt.
>
> 3) I modified the ALC circuitry to replicate the Omni V. This was the
most
> difficult challenge of all. In attempting to replicate the symmetrical
> envelope of the Omni V, this causes an ALC power spike which is also
evident
> in the Omni V. By experimenting with various R/C values, I finally
managed
> to find a combination that offered symmetry and zero power spike.
>
> Now, my Omni Six sounds excellent. My next modification involves trailing
> the end of the keyed envelope to replicate the keying of the Drake C-Line
> and TR-7. Basically, this involves modifying the integrator circuit on
the
> Omni's Control Board. The trick here is to extend the falling edge while
> keeping the TD and T voltages synchronized with the rest of the
transceiver.
>
> -Paul, W9AC
>
> ----- Original Message -----
> From: <DK2GZ@aol.com>
> To: <tentec@contesting.com>
> Sent: Monday, April 30, 2001 8:36 AM
> Subject: [TenTec] Chirpy CW-sound on an OMNI 6+
>
>
> >
> > Hello,
> >
> > i am using a OMNI 6+ and think the cw keying sounds
> > a little chirpy.
> > The little chirp is on all bands, also using low power (abt 10 watt
> out).It
> > is not the power supply!
> >
> > Checked the sound on a second receiver.
> >
> > Hw?
> >
> > 73 de Harry, DK2GZ
> >
> > --
> > FAQ on WWW: http://www.contesting.com/FAQ/tentec
> > Submissions: tentec@contesting.com
> > Administrative requests: tentec-REQUEST@contesting.com
> > Problems: owner-tentec@contesting.com
> >
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/tentec
> Submissions: tentec@contesting.com
> Administrative requests: tentec-REQUEST@contesting.com
> Problems: owner-tentec@contesting.com
>
--
FAQ on WWW: http://www.contesting.com/FAQ/tentec
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