[RFI] 12vdc native laptop

Jimk8mr at aol.com Jimk8mr at aol.com
Wed May 24 11:27:13 EDT 2006

In a message dated 5/24/06 11:02:28 AM Eastern Daylight Time,  
JimMiller at STL-OnLine.Net writes:

Looks  like way too elaborate a setup and way too many problems and not
enough  power.  Easy way that has worked for 15 years for me is to just  buy
one of the 12v to 120v inverters and use it in the car.  I have  not been
bothered by RFI problems.

Wow, that's not my experience.  The 300 watt inverter I used put out  tons of 
RFI, at least on HF.  I never tried it at VHF.
My inverter, a cheap one, makes a "modified sine wave".  That's  
marketing-ese for "square wave", of about 90 volts peak, or the same RMS value  as a 120 
volt sine wave.
The good news is that a "Car Adapter", i.e. a 12 volt to 18 volt DC-DC  
converter, is totally quiet. 
One observation:  I have always powered it from its own battery,  mostly 
because I had a supply of commercial UPS pullout 12 volt 26 AH batteries.  It was 
easier to use one of these batteries than to tie it into the car's  electrical 
system.  A friend tried a car adapter with little or no  improvement in RFI 
levels while powered from the car electrical system.   When he went to a 
separate battery the noise disappeared.
And yes, the DC-AC inverter was also powered from its own battery.
73  -  Jim  K8MR

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