How to ground a Mac

[ky1rk]

For some reason, when I have my MacMini connected via USB to a serial port on my Elecraft K3 transceiver, there is a ground voltage variance that is causing havoc with the transceiver and burning out the choke. I have been advised by Elecraft to effect star grounding scheme with the Mac and the transceiver to an outside ground to alleviate this problem:

"Essentially, all this grounding discussion boils down to:

1) The objective of Star Grounding is to keep all chassis of all gear in the shack at the same voltage level.

2) This is accomplished by connecting the chassis of each device with a single wire and then bringing those wires to one, common connection that then runs to the main ground of the residence. Here's a generic picture of this description - it really appears as a 'star' grounding scheme, no?"

So, how do I attach the Mac to a ground?

 

[prcguy]

Does the MacMini have a three prong power cable, a two prong or a separate power supply? If it has a three prong it should be grounded to the same potential as the power supply for your K3. If its floating via a 2 prong power cord then there would have to be another ground path from something external connected to your mac.

Your monitor also plugs into the MiniMac and if it has a grounded power cord it would be in common with the MiniMac via the video cable.

Usually there is not enough difference in wall outlet ground potentials within a residence but you can have a huge difference in ground potential from your antenna system. If your antenna mast or coax is grounded out in the yard and not bonded to the main house ground you can sometimes have enough voltage difference between the antenna ground and radio ground to feel a shock when you unplug your antenna. Take note of every power, ground and signal connection in your station and let us know what you find.
prcguy

For some reason, when I have my MacMini connected via USB to a serial port on my Elecraft K3 transceiver, there is a ground voltage variance that is causing havoc with the transceiver and burning out the choke. I have been advised by Elecraft to effect star grounding scheme with the Mac and the transceiver to an outside ground to alleviate this problem:

"Essentially, all this grounding discussion boils down to:

1) The objective of Star Grounding is to keep all chassis of all gear in the shack at the same voltage level.

2) This is accomplished by connecting the chassis of each device with a single wire and then bringing those wires to one, common connection that then runs to the main ground of the residence. Here's a generic picture of this description - it really appears as a 'star' grounding scheme, no?"

So, how do I attach the Mac to a ground?

 

[KE5MC]

If you have a model similar to what is currently shown on the apple webpage I would try the following.

Poke around with a ohm-meter to ensure the metal shell of the USB ports on the mac is part of the internal common inside the enclosure. If so... then sacrifice a USB cable using the metal shell on the cable as your connection into the mac and the connection leading back to your star connection point.

I get common mode current interacting with your Elecraft radio during transmit, but not sure what to think about the choke burning out.

If it really is an AC power issue one quick check is to make sure all your radio and computer equipment is powered from the same outlet. If not then its possible two different outlet in the same room are on different halves of your incoming AC power or the AC ground running back to the power panel is different length and route in the house walls.

Is the havoc only during transmit and if so which antenna? Also could you explain or give more details about the choke.

Mike, KE5MC