Hi Svend, I do not normally use the KUSB but I have just tried a simple experiment. I measured the change in noise in the following conditions:
PR6 - ON PRE - OFF AGC - OFF K3 - SSB mode, 2k7 BW ANTENNA terminated with 50 ohm. Nothing connected to KIO3: +0dBV K3 <> RS232 cable <> PC communicating with K3: +1dBV K3 <> KUSB <> PC communicating with K3: +10dBV K3 <> RS232 cable <> KUSB <> PC communicating with K3: +0dBV All readings +/- 0.1 to 0.2dBV My RS232 cable home made to K9YC design using CAT6 UTP cable is approximately 3 metres long. The presence of band noise naturally masks much of the PC noise but the increase in background noise level at this QTH when connecting the KUSB alone is still approximately +3dBV. With band noise I do not detect any increase in noise due to the RS232 cable alone. With the PR6 OFF and the K3 internal pre-amp on, noise from the KUSB is approximately +.3dBV. It seems in my configuration PC noise is least with K3 <> RS232 cable <> KUSB <> PC combination. Interesting. Maybe others would like to try and replicate this, perhaps using better test equipment than that built into the K3. It might be worth testing to see if this reduction in KUSB noise can be achieved with a much shorter RS232 tail to the K9YC design or even an appropriately wired back to back RS232 gender changer. This set me thinking that it might be a good idea to make a short cable for the K2 I/O to enable use of the KUSB or a regular RS232 cable without the danger of damage to the K2 I/O. I have not had much opportunity to play with the PR6 due to lack of 6M activity here at present other than EME. Regards, Mike VP8NO ----- Original Message ----- From: "Svend Spanget" <[email protected]> To: "Mike Harris" <[email protected]> Sent: Wednesday, August 05, 2009 5:54 AM Subject: Re: [Elecraft] Noise with KUSB Hi Mike. Thank you for answering! I have the KUSB adapter from Elecraft. Do you suggest that I make a short cable like you did between the K3 and the KUSB? The noise is specially irritating on 6 m. I don't have a preamp yet, but building one is on my to-do list. What is your experience with PR6? After I discovered the source it has become clear to me, that the noise is on all bands more or less.... My old laptop has a serial port, but I went for the USB solution because I plan to buy a new PC, which likely will only have USB ports. It is not grounded though - I will see if there is possibility to ground the PC. Lots of 73's de Svend, OZ7UV ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
