Transiever Noise from Laptop Power Supply

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Murphy625

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I have an ICOM746 (non-pro) and a laptop computer.

The ICOM's headphone jack is plugged into the laptop via a USB sound card because my laptop doesn't have all the normal sound jacks.

Anyhow, if I plug the power supply into the laptop to charge the battery, its somehow inducing so much noise into the radio that listening becomes impossible. The noise drowns out any signal I'm receiving.

Is there a solution to this? Is it because of the junky power supply that came with the laptop or is there something else going on?

I should note that the radio is powered by an isolated (not being charged) 12 volt battery.

I had considered installing a jumper from the 12 volt negative on the battery to the ground plug the laptop is using but not certain that would make any difference.

Maybe a ferrite ring on the power supply cord?

Some kind of DC-DC isolation ?
 

jonwienke

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Your best bet is a different laptop power supply with better RFI filtering. Putting ferrites on the cords is not nearly as effective as designing the circuit to not emit RFI in the first place.
 

Murphy625

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Your best bet is a different laptop power supply with better RFI filtering. Putting ferrites on the cords is not nearly as effective as designing the circuit to not emit RFI in the first place.

How do I know the next one I buy won't do the same thing? Its a panasonic laptop that needs a 70 watt power supply at 16 volts.
 

jonwienke

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It's a crapshoot, unless you can find reviews addressing RFI.

But as a general rule, name-brand power supplies from reputable manufacturers will have fewer RFI issues.
 

Murphy625

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Instead of fewer issues, isn't there some way to just eliminate them with some kind of isolation?

Chargers for my laptop are cheap if I want a noisy Chinese unit, but the original Panasonic chargers are like $60 + shipping..

There has to be another option...
 

jonwienke

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You can try adding extra ferrites on the input and output cords and you may get lucky. Or you may not.

The engineering that goes into suppressing RFI at the source is part of the reason why the name-brand supply costs $60.
 

Murphy625

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You can try adding extra ferrites on the input and output cords and you may get lucky. Or you may not.

The engineering that goes into suppressing RFI at the source is part of the reason why the name-brand supply costs $60.

Thanks for your help.. You're just full of good news..

I guess I'm just going to have to charge it when not in use..
 

ipfd320

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We Had the Same Problem During Field Day 2 Yrs Ago--The Club was Using Aftermarket Chargers--last Year we got OEM Power Supplies from h/p and the RFI Stopped---I Would Suggest Getting a New One from the Company the Computer is From

Stay Away from the Aftermarket Amazon Junk
 

Golay

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I'm curious how close the radio and computer are. Are they next to each other? Do they need to be? Can you separate them a good 8-10' while charging. If it was me, I would try snap-on ferrites. Cheap to buy, if it don't resolve the issue, you're not out much. But like jonwienke says you get what you pay for. Does the charging cable for the computer have ferrites molded into the cable already? You get what you pay for.
 

Murphy625

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I'm using a Panasonic laptop but it does have a cheap Chinese power brick for charging.

Been wondering if the RFI is radiating from the brick itself or if its being transmitted down the DC power cord.
I was thinking of wrapping it in tinfoil and grounding the foil to see if it would absorb the RFI. I also have a bunch of copper wire shielding.. it looks and acts like Chinese finger cuffs and is very similar to the shielding material inside coax cable.
 

majoco

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I'm using a Panasonic laptop but it does have a cheap Chinese power brick for charging.
Bingo! There you go. Get a linear charger, one with transformer in, there's nothing special about them, just normal DC unit preferably in a metal box, doesn't have to be regulated and I doubt if it needs to supply 60watts at 16 volts, that about 5Amps.
 
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