[Elecraft] RX IQ USB Noise

[Don Wilhelm]

You are concentrating on the "green-wire ground".
Instead concentrate on running a heavy wire or braid in parallel with 
your audio cables - it works.  It may be difficult to get a chassis 
ground on the laptop but look for a jackscrew on one of the D-shell 
connectors.  Worst case, run a wire around the shell of one of the audio 
cables at the laptop end and connect the bonding wire to that.

What that bonding accomplishes is two things - it places the connected 
pieces of equipment at the same chassis potential, and secondly it 
provides a path for hum, buzz and noise from the chassis of one piece of 
equipment to the other.
Consider that in most electronic gear, the connectors are "grounded" to 
the PC board(s) inside.  Any hum, buzz and noise that is picked up by 
the shield of the connecting cables will be conducted onto the ground 
plane of the PC boards.  The bonding wire conducts much of that garbage 
onto the outside outside of the equipment enclosure where it will be 
isolated from the working electronics.

As far as the ground rod goes, I trust you have that ground rod 
connected (outside) to the utility entry ground rod with heavy wire - #6 
but #4 is preferred.  That is required not only to meet NEC 
requirements, but also for your personal safety.  That ground is for AC 
mains and lightning safety - it is not a sink for hum, buzz and RF.

73,
Don W3FPR

On 8/31/2016 3:23 PM, Enzo Adrian-Reyes wrote:
> This would be hard but I can see how that could happen.
> The KX3 and the laptop use 2 prong connectors and this still happens, the
> macbook pro has a grounded power plug
> but this still happens.
>
> The stupid thing is they all share the same power board, so in theory they
> should all be sharing the same green wire.
>
> However
>
> The KX3 chassis is connected to a ground system independent than the
> electrical ground, the same way I thought hams connected their radio
> equipment to ground (through a ground rod). The problem I have is that I
> live near KVA power lines, and they induce a current on the shield of the
> coax, which if I dont ground the KX3 causes electrical build it which I can
> sense with my finger.
>
> So given what you have said the ground of the KX3 chassis is connected to
> the ground system for the radio, and this is causing the loop.
> However this means I cannot do what you suggest, as the ground in all the
> plugged elements is already connected to the green wire, except the KX3
> whose power supply is a double isolated, except the chassis which is
> connected to the radio ground.
>
> I do not know how to solve this, my only work around for this would be to
> try to isolate the incoming current with arrestors at the entrance of the
> shack, but that might not get rid of this current.
>
> Regards
>
>
> On Thu, Sep 1, 2016 at 3:06 AM, Jim Brown <jim at audiosystemsgroup.com> wrote:
>
>> Loop is absolutely the wrong way to view this problem, and transformers
>> are NOT the easiest or cheapest solution.
>>
>> The solution is 1) proper chassis-to-chassis BONDING between all of the
>> equipment being interconnected and 2) get power for all of the
>> interconnected equipment from the same mains outlet, or from outlets that
>> share the same "green wire" (what is called the "protective earth" in
>> Europe).
>>
>> 73, Jim K9YC
>>
>>