[Elecraft] Accurate QRP Wattmeters?

[W3FPR - Don Wilhelm]

Jay,

I may have answered this already on QRP-L, but I find the most accurate way
to determine power output is to use a good 50 ohm resistive load (check it
with an antenna analyzer or use the Elecraft DL1).  Measure the RF voltage
across the 50 ohm load (RF Probe reads in Vrms while a 'scope will show you
Vp-p), then calculate the power.  I use this procedure to calibrate or check
wattmeters.  I don't trust any wattmeter (including a Bird) until I have
verified that it is reading correctly - some can be off by as much as 20%
and still meet their specs (2 watts on a 10 watt scale, 20 watts on a 100
watt scale), and I can get MUCH closer than that with my known good dummy
load.

73,
Don W3FPR


> -----Original Message-----
>
> Hello List,
> I've posted my question on QRP-L and here as well- since I will
> be building
> a KX-1.
> I am looking for good ways to measure power output from my KX-1 while I am
> building it.
> What first came to mind was to set up my Tek 492 analyzer on a 2 dB scale
> and then use
> a 30 or 40 watt (high power) attenuator to measure CW power.  I
> have several
> Bird 43's
> but have never seen Bird slugs for QRP LF, MF or HF.  I think a competing
> company may
> have a through wattmeter with HF but I forget the lowest scale of
> that one.
> I have read
> the E-Ham reviews for the Oak Hills QRP wattmeter-  300 Khz to 54 MHz and
> 100mW, 1W and 10W
> scales- still thinking over the reviews.
>
> Comments on the accuracy of using the Tek 492 method, and on
> other accurate
> wattmeter options?
>
> 73
> Jay
> W6CJ
> AAR9QM
>
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