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VE2HAR > MT63 12.03.05 23:31l 91 Lines 2625 Bytes #-7310 (0) @ WW
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Subj: Re: [MT63] Crest Factors
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VE2HAR
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At 02:09 PM 3/12/2005, karl larsen wrote:
>Mark Miller wrote:
>
> >Karl,
> >
> >My setup is a Bird 4431 (model 43 with a sampling port)
> >
> Sorry I do not know that Bird 4431. What is the bandwidth of the
>sampled data? And what is it sampling? Is it sampling the power or the
>voltage?
You do know what a Bird model 43 is don't you? The 4431 has a power sample
output that is adjustable from -15 to -70 dB. It is a directional
coupler. The frequency range is from 2 to 1000 MHz.
> I assume you have a dummy load on your Bird watt meter. I did some
>peak power measurements using my Heathkit Antenna. It has a diode that
>picks off the voltage across the resistor which you can hook a scope to.
>It is quite accurate I found from testing.
>
> With the antenna it would be easy to measure the difference from the
>resting power with the transmitter turned on, and then the peak power
>with data flow.
What is this resting power? Please define.
> > and a Tektronics
> >2225 scope. I first calibrate my scope. I use a single tone to set the
> >output of my IC-746pro to 40 watts as shown on the Bird, then adjust the
> >trace on the scope for some convenient deflection. I ended up with 4
> >gradicules peak to peak. Then I fire up MT63. Since crest factor is Peak
> >voltage/RMS voltage,
> >
>Nope. The Crest factor is a Power measurement. And peak voltage is
>defined as the peak of the sine wave.
I disagree with you. The definition of crest factor is the peak-to-rms
voltage ratio of an alternating current (ac) signal. The crest factor of a
pure sine wave is 1.414. It is definitely voltage.
> I define peak power as the actual power when MT63 is being modulated
>continuously by digital data.
What do you mean by actual power?
> I'm afraid your measuring something else.
I am afraid you do not understand crest factor.
73,
Mark N5RFX
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