[time-nuts] OT: Power level reference

[J. Forster]

Scopes tend to have non-flat frequency response. I'd consider a precision
load and something like an HP 3400A True RMS meter for up to a hunderd MHz
or so.

Above 10 MHz the HP 432A would be my choice.

FWIW,
-John

===============


> At 11:41 PM 11/30/2009, Joseph Gray wrote...
>>We all have our various highly accurate frequency and perhaps time
>>references. Is there a relatively simple and inexpensive method of
>>making an accurate RF power level reference?
>>Joe Gray
>>KA5ZEC
>
> Since you're a ham, I'll assume you're primarily concerned with the
> simple case (50 ohm source impedance, sine wave, HF-VHF). Use an
> o-scope to measure the p-p voltage across a precision 50 ohm load (I
> use the Caddock thick film resistors available through Digikey, which
> are 1%, with minimal inductance).
>
> The power is then W=((Vpp/2)^2)/100
>
> Not time-nuts precision, but good "bang for the buck," and you can get
> better accuracy than a Bird wattmeter (which is only 5%), assuming you
> have a decent scope. Without an o-scope, you can make a peak detector
> and use a voltmeter, with some loss of low level accuracy.
>
> You asked for "simple and inexpensive." For higher frequencies,
> different impedances, non-sine waves, the other more expensive
> solutions are needed.
>
>
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