[Elecraft] PX3 signal artifact - still seeking a solution

[David Herring]

Jim,

Having percolated on this for a while longer, another thought comes to mind. You mentioned that you tried a ferrite snap-on on the USB cable. In order to really be effective, the USB cable would best be tightly wrapped around the sides of the snap-on in something of a serpentine or sequential fashion, not just randomly coiled up like a garden hose. I don’t know the specifics of how you did it, but I mention this in case you did the garden hose method originally…in that instance it would be a worthy exercise to rework your choke, wrapping it properly and seeing if that then makes a difference. 

Also, it’s not unheard of to need multiple snap-ons with multiple turns each to get enough impedance to choke out the unwanted signal.  Especially if you can’t get 6 to 8 passes through the center of a single snap-on.

Oh, and once you get the snap-on wound, it’s highly recommended to cinch down a zip tie around the circumference to ensure that both ends of the ferrite material inside are making good contact with each other. If there’s the slightest gap, the thing won’t work worth squat.

Hope that helps, and that at least one of these suggestions you’ve been getting on the reflector solves your artifact issue. ;-) 

73,
David - N5DCH



> On Jul 21, 2020, at 2:26 PM, Jim Brown <jim at audiosystemsgroup.com> wrote:
> 
> On 7/21/2020 11:10 AM, Ignacy wrote:
>> Perhaps the USB cable acts like an antenna.
> 
> That often happens. But it can also excite a Pin One in whatever it is connected to on either end.
>> For RFI transmitted via USB cable, try USB isolator. E.g.,
>> https://www.amazon.com/SMAKN-Isolator-Digital-Isolation-Industrial/dp/B00XXPO4UG
> 
> If you have more money than you need, perhaps. But all it takes is to wind multiple turns of the "USB antenna" through a #31 ferrite clamp-on. They cost a few bucks if you buy from industrial vendors like Arrow and hit their minimum order of $50 for anything in stock. Fill up that quantity with more ferrite cores -- most of us need them to kill noise from the dozens of sources in our own homes!
> 
> See http://k9yc.com/KillingReceiveNoise.pdf
> 
> 73, Jim K9YC
> 
> 
> 
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