eHam Forums => Computers And Software => Topic started by: AE5SB on March 22, 2010, 03:15:12 PM

Title: Mobile Laptop Noise
Post by: AE5SB on March 22, 2010, 03:15:12 PM
My Mobile Station is : IC706mk2g, Acer laptop

Problem: when I plug power to laptop I get S9 to +20 hash noise either moving or sitting still motor off.
This tells me the noise comes from laptop power source.
I have tried the power supply that came with laptop thru an inverter and using a universal car adapter....same thing. The vehicle is company so I cannot mod it BUT is there a way to cut the noise from the laptop power source???? By the way with laptop off I have may 1 s unit noise on 706.

Tnx for any help, I want to do PSK31 mobile(sitting still of course)

Title: RE: Mobile Laptop Noise
Post by: AA4PB on March 22, 2010, 03:44:32 PM
I've seen a lot of noise problems eminating from those universal car adapters which are really a 12VDC to 120VAC inverter. To make sure, run an extension cord outside and plug the laptop charger into the extension cord. If the noise goes away then its the DC/AC inverter. There are a variety of larger inverters available that have better filtering and less noise. Perhaps you can get to a store that will let you connect one to your vehicle and see if it is quiet. I solved my noise problem with a pure sine wave inverter.

Title: RE: Mobile Laptop Noise
Post by: AE5SB on March 22, 2010, 05:42:17 PM
The universal deal is a 13.8DC to 19 DC to power the laptop. I may go to a pure sine wave but hate to spend 175+ for one.....filter??? ferites ???

Title: RE: Mobile Laptop Noise
Post by: AA4PB on March 23, 2010, 09:18:39 AM
Probably the two things it needs are ferrites on the in/out leads and a metal shield around it. The one I had was 12VDC to 120VAC which then connected to the normal charger. It ran too hot to enclose it inside any type of shield.

What happens when the laptop is running from batteries (no charger or power supply connected)?

Title: RE: Mobile Laptop Noise
Post by: AE5SB on March 23, 2010, 05:09:35 PM
On battery runs great, everything works as it should. My battery is getting old so I may just have to get a new one or rebuild this one.

Title: RE: Mobile Laptop Noise
Post by: KD8FTR on March 24, 2010, 03:01:21 PM
I am experencing the same problem at home. Noise only when the laptop is plugged into the charger, any outlet. No noise from just the charger plugged in to the wall or computer on battery. I'm thinking it is the charging circut in the computer itself. A solution to one problem may help both of us here.

Title: RE: Mobile Laptop Noise
Post by: AE5SB on March 24, 2010, 03:47:20 PM
What name brand laptop do you have?? Mine is Acer Aspire 5100

Title: RE: Mobile Laptop Noise
Post by: N5NA on March 25, 2010, 08:36:06 PM
I highly recommend a Lind Electronics DC-DC adapter.  I was experiencing similar noise problems to what you describe using a no-name DC-DC adapter.  I switched to a Lind and it is totally quiet.

They're fairly expensive.  I have an older Dell notebook computer and found one on clearance then bought a backup on eBay for next to nothing.


Alan  N5NA

Title: RE: Mobile Laptop Noise
Post by: WA7NCL on March 26, 2010, 01:39:59 PM
I've done two things to eliminate this sort of problem.

1) buy a cheap inverter and rip it out of the case.  I then repackage it in a metal box with common mode ferrites and 0.01uF caps on the DC lines.  I used a commercial EMI filter can on the AC output.  With proper RF type wiring a cheap inverter is made low RFI.

2) Take the brick power supply (or an after market one) and rip it out of the plastic case.  Again add common mode ferrites, 0.01 caps, and emi filter, put it into a metal box (with a third wire ground to the box).  Now you have a low RFI computer power supply.

If you wonder if the laptop it self is noisey, you could do some experiments running it off batteries and bring it near your antennas a see if you get noise.  If you really are concerned about cable noise, add some dummy i/o cables while on batts. and see if there is noise.

If the laptop itself is noisey, that is more difficult and probably beyond where you want to go.