Get a big clamp-on ferrite and wrap the power cord through it as many times as will fit. Do that as close as you can to the back of the iMac. The iMac has a three-conductor power cord, so try and get all of the power cords for your equipment to a single power strip. This is a start at bonding the grounds, though it assumes competent construction on all your equipment, not just the iMac.
In general, Mac power supplies are built to very high standards for safety and RF interference. We’d all like the standards to be tougher, of course. The encyclopedic paper on RFI by K9YC recommends the "#31 'biggest clamp-on' (Fair-Rite #0431177081)”. http://audiosystemsgroup.com/RFI-Ham.pdf <http://audiosystemsgroup.com/RFI-Ham.pdf> Your other problem is the OCF dipole. A fundamentally unbalanced antenna is going to pick up more noise. Put the best quality choke/balun you can buy at the feed point of that thing. When I put a Balun Designs 1:1 balun on my (balanced) dipole, the noise dropped by 7 dB. This is the one I used. Their definition of “QRP” is 250 W. Their QRO baluns handle either 3 kW or 5 kW. http://www.balundesigns.com/qrp-model-1110-1-1-isolation-choke-balun-1-54-mhz/ <http://www.balundesigns.com/qrp-model-1110-1-1-isolation-choke-balun-1-54-mhz/> wunder K6WRU Walter Underwood CM87wj http://observer.wunderwood.org/ (my blog) > On Jun 5, 2016, at 5:03 AM, Joel Black <[email protected]> wrote: > > I figured out most of my problems with all the spikes on the PX3 - the > switching P/S in my iMac. To a lesser extent, I can hear the MFJ-4125 > switching P/S I use to power the KX3 and PX3. I cannot remember if I tried > looking at the spectrum using the Astron RS-35 as a power source and plugging > in the 4125 or not. I will try that today. I did use the RX SHFT and was able > to move a huge spike off the carrier. Does RX SHFT still nullify the roofing > filter or was that fixed in a F/W update? > > I’m pretty sure I can bond the KX3, PX3, and MFJ-4125 but I don’t have a > *clue* how to bond the iMac. It’s a late 2012 27” iMac. It’s an all-in-one > with *no* external screws. It’s the model with the “pregnant” bulge in the > back. However, if it means I have to go to a Windows computer, I’ll live with > the noise or build a Hackintosh. I also use this computer for other things - > editing video, etc. > > I *did* try my wife’s Mac Book Pro with the power supply plugged in and I did > not notice the P/S noise on the PX3; however, her computer is not powerful > enough to edit video unless you have time to wait. ;) > > Just to make sure I understand what I need to do: > > 1. Bond the KX3 to the power supply. > 2. Bond the KX3 to the PX3. > 3. Bond the KX3 to the computer (somehow). > 4. Bond the KX3 to the sound card (in my case, a Focusrite 2i2). > > Trying to use ASCII to draw, I’m guessing it should look like this: > > PX3————KX3———MFJ-4125 > / \ > / \ > iMac Focusrite 2i2 > > > My KX3 antenna connection goes to a 4-way switch to switch between my OCF, > NVIS, vertical, and dummy load. Does the KX3 need to be bonded to that as > well? All of the feed lines run up through the wall, into the attic, and out > a soffit vent to surge protectors attached to a ground rod. That ground rod > is bonded to house ground. The OCF and the NVIS are on a fiberglass pole in > the middle of the back yard. There is no ground rod there. The vertical is > over to the side and is bonded to a ground rod there. That ground rod is not > bonded but, from my reading, it should be. > > Does this look/sound right? Please be critical. I cannot learn unless you > tell me where I screwed up. I have pretty thick skin. ;) > > 73, > Joel - W4JBB > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
