Message-ID: <4C6FC2BD.1030100@iup.uni-heidelberg.de>
Date: Sat, 21 Aug 2010 14:12:45 +0200
From: =?ISO-8859-1?Q?Stefan_Sch=E4fer?= <schaefer@iup.uni-heidelberg.de>
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To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: OT - RF noise from PC display: LCD vs CRT
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Hi Daniele,

The older CTR monitor seems to have a "real" switch that yust disconnect 
the mains from the supply (like it should be!). As you said, there is 
QRM near the both monitors. The SMPS in the LCD monitor is active all 
the time, so there is QRM all the time but it should be just detectable 
in some 10 cm.

The question is, if and how the noise is (hopefully) decoupled from the 
cables going in and out from/to the monitor. This is essential since 
your RX antenna will not be placed in the near of the monitor, i suppose 
;-)

For example, i have very good experience with my tiny netbook as a VLF 
RX although it has a LCD display near the internal soundcard and the 
keyboard as well. So the LCD monitors are not worse in principal. EMC is 
an issue at all monitors so you have just to check the difference in 
your case.

73, cu, Stefan

Am 21.08.2010 13:16, schrieb Daniele Tincani:
> Hi LF, VLF,
> currently I have a CRT monitor which of course is a bit cumbersome 
> compared with a slim LCD one. On the other hand, I have done a very 
> simple RF noise test with an LCD TV/monitor I had in another room 
> and I have found the LCD is significantly noisier than the CRT. I have 
> simply checked the noise using a portable radio close to the screen on 
> LF (abt 300KHz) and MF (abt 900KHz).
> The LCD generates RF noise even when powered off (because of an 
> internal power supply, I suppose), while the CRT doesn't.
> As I plan to use my SDR in LF/MF in the vicinity of the PC (and my 
> poor VLF loop antenna usually sits only five meters apart), the RF 
> noise from monitor could be an important factor.
> Did you find similar or different results in your experience?
> Best regards
> Daniele
>

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Hi Daniele,<br>
<br>
The older CTR monitor seems to have a "real" switch that yust
disconnect the mains from the supply (like it should be!). As you said,
there is QRM near the both monitors. The SMPS in the LCD monitor is
active all the time, so there is QRM all the time but it should be just
detectable in some 10 cm.<br>
<br>
The question is, if and how the noise is (hopefully) decoupled from the
cables going in and out from/to the monitor. This is essential since
your RX antenna will not be placed in the near of the monitor, i
suppose ;-) <br>
<br>
For example, i have very good experience with my tiny netbook as a VLF
RX although it has a LCD display near the internal soundcard and the
keyboard as well. So the LCD monitors are not worse in principal. EMC
is an issue at all monitors so you have just to check the difference in
your case.<br>
<br>
73, cu, Stefan<br>
<br>
Am 21.08.2010 13:16, schrieb Daniele Tincani:
<blockquote cite="mid:799698.10240.qm@web111908.mail.gq1.yahoo.com"   type="cite">
  <style type="text/css"><!-- DIV {margin:0px;} --></style>
  <div style="font-family: arial,helvetica,sans-serif; font-size: 10pt;">
  <div>Hi LF, VLF,<br>
  </div>
  <div>currently I have a CRT monitor which of course is a bit
cumbersome compared with a slim LCD one. On the other hand, I have done
a very simple RF noise test with an LCD TV/monitor I had in another
room and&nbsp;I have found the LCD is significantly noisier than the CRT. I
have simply checked the noise using a portable radio close to the
screen on LF (abt 300KHz) and MF (abt 900KHz).</div>
  <div>The LCD generates RF noise even when powered off (because of an
internal power supply, I suppose), while the CRT doesn't.</div>
  <div>As I plan to use my SDR in LF/MF in the vicinity of the PC (and
my poor VLF loop antenna usually sits only five meters apart), the RF
noise from monitor could be an important factor.</div>
  <div>Did you find similar or different results in your experience?<br>
  </div>
  <div>Best regards<br>
Daniele<br>
  </div>
  </div>
  <br>
</blockquote>
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