Measuring an RF signal

U

udir

New Member

• Apr 17, 2009

• #1

Hi All,
I would like to ask for your opinion:
I need to measure an RF signal (RMS value).
Its Frequency is 1Mhz, and RMS output should be up to 100V..
I can do that easily using Scope, But I seek for simpler methood, like using an ordinary DVM .(That dosnt go for such frequency's).
I seek for "dummies" mehood.Does anyone have a clue how to do that?
Thanks
Udi

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Apr 17, 2009

• #2

Just build an RF probe to feed your meter, you will probably need to feed it from an attenuator at that voltage, depending on the diode you use.

 

unclejed613

Well-Known Member

Most Helpful Member

• Apr 17, 2009

• #3

an rf probe like this.... you may need to make a chart for it with some known RF voltages.

 

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U

udir

New Member

• Apr 17, 2009

• #4

Thanks for he quick reply!
A full rectifier bridge is something I also thought about, but you will need fast diodes for that at this Frequency?
The output would be DC or something close to that.Dont you use a capacitor at the end in order to smooth the ripple?
Udi

 

unclejed613

Well-Known Member

Most Helpful Member

• Apr 17, 2009

• #5

take a closer look.... it's there.... the only "ripple" is from modulation, but the time constant of R3C1 averages most of that out too...

 

U

udir

New Member

• Apr 17, 2009

• #6

Will these diodes fit to the frequency?

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Apr 17, 2009

• #7

udir said:

Will these diodes fit to the frequency?

Click to expand...

Should be fine at the low frequency you're using.

 

U

udir

New Member

• Apr 18, 2009

• #8

Thanks.
I will probably need to reduce the input V.
Will a simple voltage devicer be suffice?
Udi

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Apr 18, 2009

• #9

udir said:

Thanks.
I will probably need to reduce the input V.
Will a simple voltage devicer be suffice?

Click to expand...

Yes, and the diagram 'unclejed613' posted includes one - although I don't know why he used two diodes?, a simple halfwave rectifier is all that's commonly used.