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[TenTec] Paragon II RS-232 noise

To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: [TenTec] Paragon II RS-232 noise
From: Ken Brown <ken.d.brown@hawaiiantel.net>
Reply-to: ken.d.brown@hawaiiantel.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Sat, 24 Jan 2009 13:10:44 -1000
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
Thanks to all for the suggestions for finding the cause of and fixing 
the RS-232 noise in my Paragon II.

> Is the noise you are experiencing still there when you pull the RS232 
> Interface Card?
Have not tried pulling the card. Turning off the RS-232 communications 
makes the noise go away, either by stopping it through the software that 
runs it, or by disconnecting the interface cable, so I am sure removing 
the RS-232 board would also stop it.

> Maybe just needs 
> reinstallation to see if the card connector needs cleaning. A bad ground 
> perhaps? Or a poor connection at the cabinet rear connector?
>   
> I'd bet on a "pin 1 problem" at one or both ends of the cable.
>   
> Sounds like the computer and the rig are not at the same AC ground  
> potential. That is, if you measure the AC voltage between those  
> grounds, you may be surprised to see tens of volts.
I'll try that, however it is the same computer, same port, same cable 
and same grounding and power connections that I had been using with the 
Omni VI, which had no detectable noise at any baud rate setting. The 
Paragon II has a fixed rate of 1200 baud, and each data burst lasts 
longer than with 4800 or 9600 baud I was using with the Omni VI. That is 
only four to eight times longer, so I would have still heard a buzz and 
not just a click if the Omni VI generated a noise by the same mechanism.
> Also look at the simple bonding recommended between the chassis of 
> the rig and the chassis of the computer.
Again, since the only thing that has changed is the radio, and none of 
the cables or the computer have changed, I think any "pin 1 problem" or 
grounding issue causing this would have to be inside the Paragon II.

> Could be RFI coming from 1 or more places to there.
Not a single RF or IF control in the rig makes any change in the noise 
from the RS-232 communications, so it may not be RF noise at all. At 
least it is not radiated RF noise getting picked up by RF or IF stages 
in the rig. Only the AF volume and tone controls change the sound of the 
noise. I'm more inclined to believe it is getting into the audio stages 
though the DC power distribution, or due to a grounding fault or "pin 1 
problem."

Not going to get resolved until after the 160 CW contest. I'll let you 
know what I find.

Thanks again for the suggestions.

DE N6KB


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