[Elecraft] RFI, KUSB and MFJ-4225

[Joe Subich, W4TV]

 > Can KUSB be damaged to produce RFI yet be functional as an adapter?

*ANY* USB adapter will generate a lot of RFI and continue to work
properly if the shield of the USB cable is open or the shell of
the motherboard USB connector is not properly bonded to the circuit
board groundplane.

The first thing to try when encountering RFI with a USB adapter or
peripheral is to replace the cable.  The second thing is to use a
#31 mix toroid of the appropriate size and wind the USB cable through
it four or five times (preferably one toroid on each end of the cable
if the cable is long enough).

73,

    ... Joe, W4TV


On 10/5/2010 8:38 PM, Ignacy wrote:
>
> I am trying to clean RFI on 160m in anticipation of the contest season.
>
> When KUSB is connected to K3, it emits white noise of about 5 Khz BW around
> 1833. I attributed it to U-verse. The noise is there when KUSB is fully
> inserted into K3 but no noise when only the grounds are connected.  The
> noise is some 10 db above band noise when using K9AY that is some 100 ft
> away. A replacement USB adapter is quiet. I used KUSB before it was more RFI
> proof. Can KUSB be damaged to produce RFI yet be functional as an adapter?
>
> MFJ-4225 generates a 10db noise on 160m. Can a simple filter cure the
> problem or is it better to get a linear PS?
>
> Ignacy, NO9E
>
>