My understanding is that a USB port looks for the voltage dip caused by connecting your device - USB devices are supposed to have a capacitor on the +5 line just to cause a surge of current on connection. If you re-plug before it discharges, the port probably will not initialize properly.
The other issue with the URI is that it basically connects the DC ground of the computer through to the DC ground of the radio. There are some 600 nH chokes that don't do much of anything below VHF frequencies. With one setup, I had an audio hum problem caused by ground loop currents. Connecting a short, direct, #10 wire between the radio chassis and the computer chassis neatly fixed this. It might help a bit with HF RFI too, possibly in addition to the ferrites on the other cables. The RF would still flow, but not through the URI.
73
Ken
Attached Message
From:
Geoff <ars.w5omr(a)gmail.com>
To:
app_rpt-users(a)ohnosec.org
Subject:
Re: [App_rpt-users] Loosing TX
Date:
Mon, 10 Feb 2014 12:03:20 -0600
On 02/10/2014 08:34 PM, Doug Crompton wrote:
Another thing to consider on the DMK is RFI. They are very susceptible to it especially higher power HF but be aware that any RF could cause problems. I have had this happen at two different locations. The fix was ferrites on the leads in and out. One on each lead worked for me but more may be necessary depending on the severity. You can also wrap multiple turns through a single ferrite if they fit.
This shows up a a locked interface and usb error messages that in my case specifically said EMI? It might not always catch that it is an EMI problem though so other errors might indicate the same thing.
Since the DMK is nothing more than a fancy USB sound FOB I suspect any FOB might have this problem. Lead length both audio and USB would also be a factor.
Agreed.
I am curious, though, what voltage is sent back to the USB buss from the device.
My reasoning is, that in -my- case, when this happened, I noticed that if I pulled the USB cord, let it set for 15 or 20 seconds, then plugged it back in, the green light lit up, and as soon as it Transmitted, that URI died, again. Shutting down the machine, to the point of letting the caps discharge, etc, then bringing everything back up, plugged in, all worked flawlessly...
until, at least, I RF'ed the system again with HF signals from 75 and/or 40m.... ~sigh~
73 = Best Regards,
-Geoff/W5OMR
