Yes and most power meters are voltage sensing instruments which are
calibrated to a specific value or load. Thus is the load being used may
not be the identical value to which it was calibrated, hence another
error enters the equation.
To wit, I have 3 "allegedly" 50 ohm dummy loads. Only one is actually
50 ohms but others are as low as 45 ohms and as high as 58 ohms, while
one actually measures 50.5 ohms. If one is trying to measure power
then both voltage and current should be measured with a known load and
then do the math. If you are using an antenna, it most likely is
somewhat reactive. This throws another curve into the ballpark in terms
of power measurement.
73
Bob, K4TAX
On 6/19/2018 7:15 PM, Fred Jensen wrote:
Most, if not all analog measurement devices are spec'd at % of full
scale which can lead to high absolute variances if the levels being
measured are significantly below full scale. A Bird with a 100W slug
accurate to 10% of full scale [+/- 5W] would be within spec if it
indicated a real 10 W signal at 5 W. Many folks would say, "My K2/10
will only produce half the power it should." Most digital
measurements involve processing circuitry/computation, again which can
introduce errors in the lower end of a range, and be dependent on
frequency as well.
Mathematics can be hard. Arithmetic can be tricky. [:-)
73,
Fred ["Skip"] K6DGW
Sparks NV DM09dn
Washoe County
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