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Jim,
In my experience, (I do EMC for a living), the DC to DC adapters are
even worse than the AC power cubes. One of the reasons is because they
do not have to be tested for conducted emissions that they put back on
to the power mains. No AC power mains no testing needed. We do however
test them for radiated emissions and they always are bad in the 30-100
MHz range where radiated emissions are measured.
My employer will have a new 12 to 18.5 VDC, 65 Watt adapter out in the
next quarter that will be very quiet. I will update when I have a
model number and post it to the group.
BTW, the adapters that use 12 VDC to generate 120 AC are an even worse
solution because they generate just as much noise in addition to the
noise from the standard AC cube.
Earl
N5TU
> Message: 1
> From: Jimk8mr@aol.com
To: <rfi@contesting.com>
> Date: Wed, 26 Dec 2001 10:32:29 EST
> To: rfi@contesting.com
> Subject: [RFI] Laptop Car Adapter Power Supplies
>
> For my mobile contest operations in the past few years I have been powering
> my laptop with an 12VDC to 110VAC inverter that runs the usual 110VAC power
> supply. Not surprisingly, the inverter can be a major RF noise generator.
>
> Does anyone have RFI experience with the 12 volt car adapter power supplies
> for laptops? Are they quieter than the typical 12-110VAC inverters? Are
> there differences between models? Any other issues relevant to using them in
> the presence of 100 watts of HF RF a few feet away?
>
> Tnx & 73,
>
> Jim K8MR
>
>
>
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Jim,
<p>In my experience, (I do EMC for a living), the DC to DC adapters are
even worse than the AC power cubes. One of the reasons is because
they do not have to be tested for conducted emissions that they put back
on to the power mains. No AC power mains no testing needed.
We do however test them for radiated emissions and they always are bad
in the 30-100 MHz range where radiated emissions are measured.
<p>My employer will have a new 12 to 18.5 VDC, 65 Watt adapter out in the
next quarter that will be very quiet. I will update when I
have a model number and post it to the group.
<p>BTW, the adapters that use 12 VDC to generate 120 AC are an even worse
solution because they generate just as much noise in addition to the noise
from the standard AC cube.
<p>Earl
<br>N5TU
<br>
<br>
<br>
<blockquote TYPE=CITE>
<pre>Message: 1
From: Jimk8mr@aol.com
To: <rfi@contesting.com>
Date: Wed, 26 Dec 2001 10:32:29 EST
To: rfi@contesting.com
Subject: [RFI] Laptop Car Adapter Power Supplies
For my mobile contest operations in the past few years I have been
powering
my laptop with an 12VDC to 110VAC inverter that runs the usual 110VAC
power
supply. Not surprisingly, the inverter can be a major RF noise
generator.
Does anyone have RFI experience with the 12 volt car adapter power
supplies
for laptops? Are they quieter than the typical 12-110VAC inverters?
Are
there differences between models? Any other issues relevant to using them
in
the presence of 100 watts of HF RF a few feet away?
Tnx & 73,
Jim K8MR
</pre>
</blockquote>
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