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Author Topic: Laptop interference with HF Rig  (Read 3468 times)
AB3QK
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Posts: 3




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« on: February 11, 2012, 08:44:39 PM »

I'm limited on space in my "shack", live in a condo.  However, my problem is my rig (IC-718) sits next to my laptop.  When I have the laptop plugged in to my ac adapter, I am getting loud noise especially noticeable on 20 Meters.  If I'm on 20m, and unplug the ac cord and run the laptop off battery, the noise level drops considerably.  Any suggestion on how to correct this problem would be greatly appreciated.  Thanks!!

73

Lou KB3LJF
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WX7G
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Posts: 6192




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« Reply #1 on: February 12, 2012, 01:39:51 AM »

A different AC adapter is a solution. Or adding suitable ferrites to the AC line cord. Or trying an MFJ-1163 AC line filter.
« Last Edit: February 12, 2012, 08:36:36 AM by WX7G » Logged
W8JX
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Posts: 6410




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« Reply #2 on: February 12, 2012, 08:18:35 AM »

Might also look at routing and positioning of power adapter relative to HF rig's power supply and power wires. 
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All posted wireless using Win 8.1 RT, a Android tablet using 4G/LTE/WiFi or Sprint Note 3.
K1JK
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Posts: 207




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« Reply #3 on: February 25, 2012, 03:24:08 PM »

hi
had the same problem with my 718  with older dell laptop
the dell had aftermarket power suply
 the got new laptop(acer) no noise form laptop
sits next to 718

jeff k
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AA4PB
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Posts: 12972




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« Reply #4 on: February 25, 2012, 03:54:14 PM »

The RFI generated in the switching type computer power supply is most likely being radiated by the DC power cord that connects the supply to the computer. I'd start by placing some ferrite beads on that cable, close to where the cable exits the supply.
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WA7NCL
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Posts: 625




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« Reply #5 on: March 04, 2012, 07:59:34 AM »

It's usually the power supply.

The first line of defense is to wind the AC power cord around a large diameter ferrite toroid with high permeability.
You want about 5 turns or so.  Adjust the number for best results. 
The use of clamp on beads is usually ineffective because the impedance of the beads is low at HF, you might have to use say 10 of them or completely cover the entire line cord for them to be effective.

The second line of defense is add another toroid to the DC output line.  Again something around 5 turns to 10 turns.

The third line of defense if you are really desperate.  You have to put the power supply in a metal box.  You need to modify the mains coupler and add an EMI filter to the AC line.  You can buy them at Digikey.  You need to ground the third wire to the box.

I usually add a toroid choke to the output wound common mode, and some bypass caps to the metal box.  You need to use radio type construction techniques.  Many times mounting is much better if you crack open the case and mount the PC board to the box with nylon spacers.  There are High Voltages so you need to use "tube type" radio techniques.

I have done the metal box mod, and it works, but you really need to be adept at safe construction of the things with high voltage.  To the point of which I think if you know enough to do as I described, I probably didn't need to tell you.

Fortunately the toroids on the input and output usually works well enough.
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