[Elecraft] K3/100 peak vs average RF power

[Jay Bromley]

Hi Bill,
Interesting stuff!

I've seen more than one PEP meter that is deadly accurate on calibration
with either CW or SSB, but not both or the other way around.  Also the
frequency response of the tone/tones used to cal the meter with are much
different than say speech or CW.  Even a mic with a lot of bass response
compared to one that has little or no bass response will affect PEP meter
readings.  Ditto on AM transmitters with good and not so good frequency
response.  I tore into a few PEP meters to have a look and see, most are
loaded with electrolytic capacitors that age fairly quickly that will affect
PEP readings, even the meter movement itself affects how things work on PEP.

After testing a few meters, I just use the ones the look cool, but keep the
scope in line for serious PEP work!  In the end, I don't worry so much with
meters except for solid carriers.  They do look nice having that wide PEP
swing.  :-)

Just some more things to ponder.

73 de w5jay/jay..




>
> After reading several posts expressing concern about low K3 RF power
> output,
> I decided to run some  tests on my own K3.
>
> Equipment used: K3/100 #0224 (2.7khz stock filter) with current MCU and
> DSP
> firmware (1.78 / 1.58); Telepost LP-100 digital vector wattmeter; Telepost
> LP-200 dummy load wattmeter; MFJ-872 peak/average wattmeter; Daiwa CN620B
> wattmeter (average reading); Elecraft 2T-gen; high quality non-reactive RF
> dummy load. No antennas. K3 ATU bypassed.
>
> The K3 was set to request 100 watts output on 14.250 Mhz USB. The 2T-gen
> was
> connected to the front mic input and mic gain adjusted to a value of 20.
> This resulted in 5 bars of ALC. Compression was set to an arbitrary (and
> low) value of 10.
>
> Results, LP-100 wattmeter: peak power measured 97.6 watts (averaged over 5
> measurements).  Set to measure average power, the LP-100 repeatedly
> measured
> about 60 watts output.
>
> Results, LP-200 dummy load wattmeter: 99-100 peak watts reported over 5
> measurments.
>
> Results, MFJ-872 Peak/Average wattmeter: 'Peak' reading on analog scale -
> 85
> watts.  'Average' reading on analog scale - 55 watts.
>
> Results, Daiwa CN620B average-reading wattmeter:  40 watts per analog
> scale.
>
> While the LP-100 and 200 were in close agreement, keep in mind that I
> calibrated them myself against a nominal 25 RF peak watts as determined by
> an accurate oscilloscope. The other two instruments reported somewhat
> disparate power values compared to the LP-100/200 and one another.  I'm
> not
> drawing any definite conclusions from these results; I'm simply reporting
> them out in the event some readers might find them helpful or interesting.
>
> 73,
> Bill, WA4KBD
> -- 
> View this message in context:
> http://www.nabble.com/K3-100-peak-vs-average-RF-power-output-tests-tp16996450p16996450.html
> Sent from the Elecraft mailing list archive at Nabble.com.
>
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