If I recall correctly, the VI+'s and maybe the VI's as well, had these
residual noises. Individual radios had more or less of this noise. A lot
of work was done to try to fix it, and the leading answer was to re-orient
the cables interconnecting boards, etc., in a way that reduced that noise
pickup. I don't remember what the subject of those threads was, but it was
covered some time back (resulting in variable results) quite a while ago.
I'm thinking it was maybe in the late 1990's or so?
73, Duane
Duane Calvin, AC5AA
Austin, Texas
www.ac5aa.com
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Barry N1EU
Sent: Sunday, April 05, 2015 9:12 AM
To: Discussion of Ten-Tec Equipment
Subject: [TenTec] Digital noise in Omni 6+ audio
There's a fair amount of low-level objectionable noises (high-pitched
tones, tuning encoder noise, etc) in the Omni 6+ receive audio. It
detracts from what is otherwise a fantastic sounding receiver. Using the
LP function gives some, but not complete, relief to the high-pitched tones.
Has anybody investigated/analyzed this to any degree? I would think that
the noise must be introduced where the IF/AF board audio loops to the CODEC
(via cables 54/56) on the logic board for dsp processing. I pulled the
logic board and was surprised to find that the CODEC chip's "analog" ground
U11-17/18 is isolated from the rest of the logic board and is only
connected to the shield of cables 54/56. Yet the shield of cables 54/56 IS
connected to chassis ground back on the IF/AF board. This just leaves me
scratching my head - has anybody else looked at this circuit or can
otherwise comment on this grounding scheme?
I also looked at the +5V supply to the CODEC chip U11 and no glaring issues
jumped out at me.
73, Barry N1EU
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|