[Elecraft] PX3 signal artifact - still seeking a solution

[Philip Alley]

Jim,

This sounds a lot like a problem I was experiencing with my KX3 while operating FT8.  I was getting pulsating noise on the signal sent to the KX3 from my MacBook Pro laptop.  I tried all the suggestions including bonding the computer and putting ferrites on all signal and power leads with no improvement.  I finally noticed that Elecraft KXUSB cable connected from PX3 to the laptop for rig control has an LED which blinks at a rate (almost exactly once per second) with corresponds to the noise heard.  

On the MacBook Pro I was using a port adapter which allows connecting a HDMI cable, a USB cable and an apple Lightning power cable to one of the 4 USB-C (Lightning) ports on the laptop.  By simply moving the power cable from the adapter to a separate port the noise completely disappeared.  Since you mention that your foul signal disappears when you disconnect the USB cable from your laptop I suspect you may be suffering the same problem.  In my case, apparently when the LED pulses some of the power supply noise is coupled into the USB port and contaminates the signals.  I was worried about transmit signals and did not see if any artifacts were showing on the PX during receive.

Phil -AA2EA
Louisville KY

> 
>> On Jul 21, 2020, at 9:07 AM, James Smallwood via Elecraft <elecraft at mailman.qth.net> wrote:
>> 
>>> My station consists of a KX3 / PX3 connected via 100 ft of DX Engineering RG-8/U Low-Loss coax through an Alpha Delta antenna switch to a Balun Solutions 4:1 Unun tied to a 31 ft vertical antenna. The antenna and unun are grounded via a copper rod driven 3 feet into sandy soil in South Florida. The entire station is grounded to the ground system of my house by a single copper ground wire which is about 7 ft long. Each piece of station gear (including the antenna switch) is separately grounded to a 2 foot copper pipe tied to that ground. I run the station off a 12v 3Ah Bionenno LiPO battery.
>>> 
>>> My question concerns a visual signal artifact of about 5-7dB strength that appears on my PX3, just off the frequency to which I am tuned. The artifact has 2 peaks when viewed at higher resolution. The artifact (which has no audio component) appears to be closely associated with a new Elecraft-provided USB cable connecting my HP Pavillion PC to my PX3. Once the USB cable is disconnected from the PC, the artifact disappears from the PX3 display. As soon as the cable is reconnected, the artifact reappears.The artifact appears regardless of other signals being present.
>>> 
>>> I recently purchased and installed a range of Palomar Engineers ferrite snap-ons (>>Mix 31<<) which failed to mitigate this artifact. I coiled as much of the USB cable as possible then clipped on the ferrite beads. This had no effect. I placed additional ferrite beads on other wires and cables associated with my station, but observed no impact on the artifact.
>>> 
>>> I am wondering whether I may need a different mix ferrite. Based on what I have shared here, do other solutions present themselves?
>> 
>>> Thanks for sharing any insights or suggestions.
>>> 
>>> Jim - N7RCS
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