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Voltage measurement on RF cable - RF Cafe Forums
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| Ted1234
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Post subject: Voltage measurement on RF cable
Posted: Thu Oct 20, 2005 4:03 pm
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I have a piece of RG58 going into an into an o-scope
with a 100 MHz BW. The signal is a sinewave (almost)
and I know the power out of my source (10 MHz) is
+10 dBm. Problem is the o-scope is reading about
exactly twice the voltage I expect to see (which
is 2 Vpk-pk). I'm measuring 4 Vpk-pk. Any ideas
what might be going on. Thanks.
--- Ted
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kanling |
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Post subject:
Posted: Thu Oct 20, 2005 4:08 pm
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| Colonel |
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Joined: Mon Jul 18, 2005
4:31 pm
Posts: 40
Location: Baltimore, MD
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I'll bet your scope's input is set to the high impedance
mode. Make sure it is set to be a 50 Ohm load. You
are exactly right to be expecting about 2 Vpp.
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Guest |
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Post subject:
Posted: Fri Oct 21, 2005 7:17 am
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Agreed, your scope impedance is not 50 ohms. If
you do not have an option for 50 ohms, place a 50
ohm resistor in parallel between clip leads.
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Ted1234 |
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Post subject:
Posted: Fri Oct 21, 2005 10:24 am
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kanling wrote:
I'll bet your scope's input is set to the high
impedance mode. Make sure it is set to be a
50 Ohm load. You are exactly right to be expecting
about 2 Vpp.
Thanks kanling - you are exactly right
I can't believe I was dumb enough to not
think of that.
Ted
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Posted 11/12/2012
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