Don and the group,
I did another round of work on the Omni 6 after posting that first
preliminary mod and I came away more pessimistic after further work
with the Omni 6 rx audio. When I bypassed all the circuitry after the
product detector, I found the noise level just too high (i,e,
stop-band was to shallow). The Omni 6 seems to depend on the dsp to
do some needed low pass filtering on the rx audio. There also seems
to be a tendency for the 6.3Mhz filter to introduce ripple into the
pass-band.
73, Barry N1EU
On Sun, Feb 6, 2011 at 5:41 PM, Don Rasmussen <wb8yqj@yahoo.com> wrote:
> Dale,
>
> The OMNI 6+ will never have the audiophile range of fidelity that EAGLE,
> Orion, or OMNI 7 has - I think that's what Barry N1EU is indicating.
>
> If you already did the Inrad mod (solder a couple parts on the OMNI) AND you
> have the Inrad 2.8 filters (there are two of them), here is something to try.
>
> I found a mod on Barry's website that takes OMNI 6+ out of that audio
> restricted category you are referring to, which is prominant even with the
> Inrad 2.8 filters and the Inrad mod combined.
>
> I have a pigtail coming out of the back of the OMNI with a sub-mini female
> connection. I plug the amplified speakers from my computer (has subwoofer)
> into this jack when I want to hear the expanded audio. For CW it is a non
> issue, the CW is best coming out of the normal AF chain. The AGC and
> selectivity of the OMNI 6+ is the best I have used, just at times want a
> little better audio quality.
>
> The OMNI 6+ DSP comes further down in the chain than the audio take off, that
> is the reason for the improvement, you are taking the DSP out of the line and
> that has some hi-lo end rolloff.
>
> The DSP also performs the auto notch and FM functions so you dont have that
> when using the audio out mod. If you have a volume control on your amplified
> speakers you can turn that down and turn up the AF gain on the OMNI to
> activate the notch, do FM, etc.
>
> =======
> Omni VI
> =======
>
> The stock Omni VI(+) suffers from a very constricted passband in ssb. ARRL
> measured about 1600hz in their review. After experimenting a bit, I found a
> way to completely open the passband up to the full width of the xtal filters.
> For those seeking hi-fi ssb rx audio from the Omni VI, and who are willing
> o amplify the audio externally, a night and day improvement can be had from
> tapping the product detector audio off U3-6 on the if/af board through a 1uF
> capacitor tack soldered to the pin, and a shielded cable brought out for
> amplification. It is a requirement that you then adjust C10/C12 on the TX
> Audio board to optimize the receive passband.
>
> The Inrad 2.8Khz filters are really a necessity to complete the "mod" for the
> Omni VI. It goes without saying that the notch filter, dsp, sidetone, fm,
> etc. are bypassed with this audio output.
>
> Good Luck and happy listening!
>
> PS - (You dont want a 6 khz filter from Inrad)
>
> 73,
> Don
>
>
>
> [TenTec] audio on Omni-VI+
> from [yash] [Permanent Link][Original]
>
> To: tentec@contesting.com
> Subject: [TenTec] audio on Omni-VI+
> From: yash@aol.com
> Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
> Date: Sun, 06 Feb 2011 09:31:37 -0500
> List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
>
> Have been using my ,new to me ,Omni VI+ for a few weeks,like the rig,hard to
> fault for a 10+ year old rig. I have one problem that I would like to change.
> The audio quality. In stock form the rig sounds "nasally" to me ,constricted
> and choppy. I installed the Inrad audio kit ,2 caps and 1 resister,it made a
> nice change in the quality of the audio. I noticed that INrad also mentions
> changing the OEM 6 MHz filter with a #755 of their design. Has anyone done
> this filter change? Is there another route to getting the audio sounding full
> and clean with this rig? Other than the audio the VI+ is great.
> thanks
> dale wt4t
>
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