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 betwen the 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
>
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>
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