[TenTec] RFI from USB-to-serial adaptor cable

[d.e.warnick at comcast.net]

I'm running a Keyspan 4-port Serial adapter with no problems at all. It came up as Com 3, 4, 5, & 6 on my system under Vista. Yep, works fine on vista with MixW to my Omni VI+. Thanks to Carl for the advice
Dave
WA3MKB

-------------- Original message -------------- 
From: Rick Denney <rick at rickdenney.com> 

> Folks, 
> 
> As it turns out, I'm getting significant RFI from the USB-to-RS232 
> cable I'm using to run my RX-320. The cable clearly has some circuitry 
> in it, though it must be hiding in the molded plugs. It required a 
> devie driver that was the commonly available driver for such devices. 
> It works just fine, but when I plug it into the USB port, "band noise" 
> increases by about 2-3 S units. I can't hear anything but noise in the 
> RFI. It seems to affect 20 meters more than, say, 80 meters, but it's 
> always there. 
> 
> I have tried it with all the other devices from the computer connected 
> or disconnected, but the noise vanishes when I pull the USB plug, and 
> reappears three seconds after plugging it back in. That three-second 
> delay tells me it's a noisy processor in that cable, not something 
> like common-mode RFI on the shield (and it is a well-shielded cable 
> with a clear jacket). 
> 
> Options seem to be: Find a PCI-based RS-232 board and don't convert it 
> from USB, find an adaptor cable that doesn't create the noise, or find 
> a way to shield the adaptor cable in use. I haven't tried ferrite 
> beads or the like, but I'm sure others have experienced this same 
> issue there is an obvious answer. 
> 
> (I built the serial cable for connecting the Omni V myself, and 
> soldered the shield to the shell of the DB9 and DB25 plugs. I also 
> used metallic plug cases and well-shielded cable. There is no noise I 
> can detect emanating from that cable.) 
> 
> Advice craved and appreciated. 
> 
> Rick, KR9D 
> 
> 
> --- 
> Richard W. Denney, Jr. PE|Iteris, Inc. 
> Associate Vice President |107 Carpenter Dr. Ste 230 | 703.925.3819 
> rwd at iteris.com |Sterling, VA 20164 |Fax 703.471.1757 
> 
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