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Author Topic: LCD VS. CRT MONITOR  (Read 413 times)
W3FM
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Posts: 35




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« on: August 30, 2004, 09:46:24 PM »

I USE A BACKARD BELL 17" CRT TYPE MONITOR WHICH PRODUCES VERY LITTLE RFI.  I WOULD LIKE TO REPLACE IT WITH AN HP 19" LCD MONITOR.  CAN I EXPECT LOW RFI FROM THE LCD MONITOR ?
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KZ1X
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« Reply #1 on: August 30, 2004, 10:29:53 PM »

MY LCD MONITORS ARE TOTALLY QUIET, even when I type in all caps.

Did you know that typing in all caps MEANS YOU'RE SHOUTING?

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K7SUB
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Posts: 22




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« Reply #2 on: August 30, 2004, 11:01:04 PM »

I use 2 LCD monitors in the shack and they are totaly quiet. The CRTs they replaced did produce several "Birdies" even with the ferrite beads.
Bob
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AC5E
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« Reply #3 on: August 31, 2004, 07:35:41 AM »

There's no high voltage supply in an LCD monitor, therefore no "flyback" type horizontal deflection/HV circuit with its extremely high level of harmonics. That may or more likely may not be kept in the box.

Every LCD monitor I have come in contact with has been RF quiet. I can't say the same about some of the video cards, and especially about a couple of motherboards with on board video but if your current monitor is RF quiet an LCD should be even quieter.

73  Pete Allen  AC5E
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KB8ASO
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Posts: 71




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« Reply #4 on: August 31, 2004, 09:57:18 AM »

This is not completely true.  There is a high voltage inverter (Depending on the size of the screen there will be 1, 2 or more of them.  One per lamp.) to power the cold cathode lamps.  I have a 3 year old 15" H/P and it has just as much RFI as a CRT monitor.  Take a old AM transistor radio with you when you look at LCD monitors and test each one for RFI.  

Randy AB9GO


"There's no high voltage supply in an LCD monitor, therefore no "flyback" type horizontal deflection/HV circuit with its extremely high level of harmonics."
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WB2WIK
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Posts: 20547




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« Reply #5 on: August 31, 2004, 11:28:13 AM »

You "Backard Bell" (Packard-Bell) monitor was actually manufactured by someone else, since Packard Bell never manufactured monitors.  As such, we really don't know what you have.  (Most PC manufacturers don't manufacture their monitors.  Sony is one notable exception, for CRT monitors, and L-G is a notable exception for flat panel monitors.)

It's really hard to say what's going to be "RF quiet," and what's not.  The suggestion regarding carrying a receiver into the shop and probing around, looking for noise, is a good one that I also follow.

WB2WIK/6
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G7HEU
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Posts: 261


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« Reply #6 on: August 31, 2004, 12:29:08 PM »

I would like to agree that some TFT ( LCD ) monitors can be 'noisy'. My 15" unit is a pig on 20Mtrs.

I've fitted ferrites all over the inside wiring and clipped more onto the d.c. supply and VGA cables. There was a slight improvement but I still have to turn it off to use 20Mtrs.

Here's something to think about - when I used a coax fed G5RV the problem was worst on 40Mtrs. Then I converted it to a doublet with a big, open, balanced tuner. That 'cured' the problem on 40Mtrs but made it much worse on 20.

Steve
M0HEU / G7HEU.

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W5WJP
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Posts: 157




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« Reply #7 on: August 31, 2004, 09:15:48 PM »

I use a an old IBM Thinkpad in the shack and it is totally quiet on all bands. I have never had a LCD monitor give of any noise. I also have a couple of el cheapo (if there is such a thing in LCD's) and none of them give off any noise.
YMMV.


73,
W5WJP

 
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KC2MMI
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Posts: 621




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« Reply #8 on: September 01, 2004, 12:57:55 AM »

Flat-panel PLASMA monitors are notorious RFI pigs.

LCD monitors usually are not.

The plasma monitors are usually the very big, very bright, kilobuck models sold for "home theatre".
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WA2JJH
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« Reply #9 on: September 07, 2004, 11:14:08 AM »

The newer LCD monitors have a well shielded voltage inverter for the flouresent back light.

  I have seen 17" LCD's down to the under $200 level.

The MAJOR brands have little or no RFI.

  If you have an H-T that does HF-RX, go to a store and see whats what.

I like the Panasonic and Sonys.

  The better monitors are in carbon fiber cases as well.

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