[Elecraft] KUSB Noise Query - K3

[Buck - k4ia]

I have found that I must be sure to screw in (not just plug in)  the 
serial connector on the back of the K3.  If I don't, I will hear a 
pulsed rushing noise from the USB.


Buck
k4ia

On 12/13/2012 12:53 PM, Matthew Zilmer wrote:
> USB uses differential signaling.  Your problem may not be conductive noise, but instead it could be radiated directly from the adapter, where the ferrite won't help.
>
> KeySpan makes a USB - serial adapter that is pretty much noise-free.  Its model  is HS19, I think.
>
> Matt Zilmer
> Consultant - Product Management Dept.
> Magellan Navigation / MiTAC Digital Corp.
> Tel: (909) 394-6052
> Cell: (909) 730-6552
> In status quo voluntas non sufficit
>
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of john petters
> Sent: Thursday, December 13, 2012 9:25 AM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] KUSB Noise Query - K3
>
> Hi Folks,
> I posted a query about K3 Serial ports a few months back - we could not get the K3 to work properly with the RS232 connection. It turned out to be a fault with the sound card, which took out the serial connections.
> When I first built the K3, I bought a cheap Prolific USB converter, which radiates awful noise over the spectrum. I decided to bite the bullet and buy the proper lead, which arrived today.
>
> Using my Toshiba laptop, on battery power, I get a couple of s points of noise on 10M with the KUSB connected and HRD fired up. This is using my
> 2 element DJ4VM quad, which is fed with 300 ohm twin into the shack, i.e. near the laptop.
>
> On LF, I can hear the pulsing information, in sympathy with the flashing LEDs on the KUSB on 160M at quite a high level. I can even detect this when fed into a Marconi dummy load. The K3 and the tuning units are bonder to an RF earth - a copper stake about 8 feet away from the K3.
>
> I have tried choking the USB lead at the laptop end, which does reduce the noise to a degree.
>
> The question I have is - am I being unrealistic in expecting zero noise to be radiated from these adaptors?
> Does anyone else have this problem - or has anyone looked for it?
>
> It is not very noticeable on CW or SSB. To hear it best, listen in the AM mode with the AGC off. On SSB it sounds like band noise.
>
> Is this a problem JUST with USB adaptors or can I expect silence when connecting a computer via RS232 to RS232.
>
> If not we are sacrificing a low noise floor for the convenience of computer control.
>
> Any views appreciated,
>
> 73
>
>
>
>
> --
> John Petters
> www.traditional-jazz.com
> Amateur Radio Station G3YPZ
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