> On Tue, Aug 4, 2009 at 6:38 AM, Svend Spanget > <span...@privat.dk> wrote: > > > I recently discovered the source of a very annoying noise in my K3. > > When unplugging the USB cable from my USB hub the noise in the > > receiver disappears. How do I get rid of this? I am using HRD, so a > > connection to my PC is really needed... > > 73's Svend, OZ7UV
One of the most common sources of USB device related noise is a bad/open shield on the USB cable. First thing to try is a different USB cable. Since you have a hub involved, don't forget to check the cable between the computer and the hub as well as the power supply for the hub. Also make sure the computer is properly grounded to the station's common ground point and the shield has a good contact to the motherboard groundplane and the chassis. If the noise is from the RS-232 side of the USB to RS-232 converter, place a jumper across the RF choke in pin 5 of the RS-232 connector (Elecraft RF Immunity Mod - <www.elecraft.com/K3/mods/ELECRAFT_Application_Note_Improving_the_Immunity_of_ the_Rear-Panel_KIO3_RS232_and_Audio_Connectors_to_RF.pdf>. In addition, consider making your own RS-232 cable using K9YC's suggestions (CAT5 cable with pins 2,3,4 & 7 each on a separate "pair" with the other wire of each pair connected to the shell of the connector). The K9YC cable makes the RS-232 signals "balanced" and cancels any radiated noise using the "magic" of twisted pairs. 73, ... Joe, W4TV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
