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Oscilloscope HP54111D display question - NEED HELP PLEASE

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Tedyp

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Hello,
I've purchased a scope HP54111D, almost unused, and I need to measure and to display a 434MHz wave. I have 2 probes of 150MHz, (waiting for a 500MHz one), however connecting it to any signal source from 100 to 434MHz, I am getting the signal made by dots as shown in the picture. Even the square wave calibration is made of dots.
Here is the picture:

I have and use 2 analogue scopes (Tektronix) up to 150MHz without problem, meaning I can see a nice sinus wave "drawn" in continuous mode, I mean without dots, a sinusoidal line. As well, as I am modulating the 150MHz (FM), I can see in real time the modulation.
As I never used a digitizing scope before, I have no idea if I can use it for this purpose, how to get a smooth line instead dots and how to do the measurement.
Thank you for assistance in advance,
Tedyp
 

E-design

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What you are seeing are the sampling points. Look under "Display" and make sure that BW is not on. Appears that you have averaging on as well.
Also you can select the resolution. Full bandwidth you can only have 6 bits. You can choose to connect the dots as well under "Display" settings
Also check that the Chan input impedance is set to 1M Ohm with probe and not 50 Ohm and probes are properly compensated.
These old scopes are not really good for viewing modulation properties because screen update is way to slow.
 
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Tedyp

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Thank you very much for your assistance.

Look under "Display" and make sure that BW
What is exactly "BW" ?

Many thanks!
 

E-design

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BW meaning - see that Bandwidth limiter is not on
 
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Tedyp

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Thank you again Sir,
Even that I have the original manuals, I've d/led the pdf too, hopping to do a search for the word "Bandwidth" - I assume that the manual has been scanned, so I couldn't find it.
If you know where may I find any documentation about the BW limiter, I'll be more than thankful.
Best Regards,
Dr. Tedy
 

E-design

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Under "Display" tab with "Real time" selected and resolution above 6 bits you will have the bandwidth limited automatically.
 

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