[Elecraft] RF Probe measurments - K1

Mon Feb 18 19:21:00 2002

Hi Ron:

Well I thought maybe we were looking at a non-linear scale at low wattage -
or something like that ;)  I built the N5FC RF probe -
http://www.io.com/~n5fc/rfprobe2.htm - and I was very pleased with the
result.  My KAT is Rev. C .  Maybe have something to do with it.

Thanks, 

Jamie
WB4YDL

> From: "Ron D' Eau Claire" <[email protected]>
> Reply-To: <[email protected]>
> Date: Mon, 18 Feb 2002 16:03:19 -0800
> To: "Elecraft List" <[email protected]>
> Subject: RE: [Elecraft] RF Probe measurments - K1
> 
> 
>> I'm not at home right now, but the KAT manual said 14 volts.
>> Hmmm - maybe a
>> fudge factor needs to be added, but 1.8 volts ?!  Interesting when I made
>> the adjustment, the max voltage of 19 volts did agree with the formula for
>> 7.2 watts.  Go figure !
>> 
>> Jamie
>> WB4YDL
> 
> 
> Whatever the manual says, YOUR calculation is right! 15.8 vrms across a 50
> ohm load is, indeed, 5 watts (well, 4.99).
> 
> The Elecraft probe includes a scaling resistor that should give you a direct
> readout in RMS provided that you use it in a voltmeter circuit with an 1l
> megohm input resistance. The accuracy is dependent upon those resistances
> both being close so the metering circuit reports 7.07% of the d-c voltage
> across the diode in the probe.
> 
> Ron AC7AC
> K2 # 1289
> 
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