I'll appologize up front, as this thread is slightly off-topic
w/resp. to towers/antennas. EXCEPT for handling and
interpreting data from relative measurements...there it
IS relevant, and may be helpful to some. This is my last
on this topic, in any case.
Although a DMM (or any instrument)may have an absolute accuracy
which is no better than 3%, for example, it CAN be used for
data analysis at much greater resolution. That is, the DMM
may have 3 1/2 or 4 1/2 digits resolution, and provide repeatable
readings at the 0.1% level.
Saving data over time provides a time-profile (in the case of
line voltage) of the Vac swings. Now, we don't know what the
actual voltage is, better than 3%. But we DO know the range of
variation, quite closely. All it takes is ONE reading with a
calibrator, or comparison with more precise meter, to relate
that time-variant dataset to absolute levels.
Consider a receiver, with an S meter which is non-linear, by
design. But possibly not truly logarithmic...so you don't know
what it does, over its range.
Can you make antenna pattern measurements using it as an indicator?
There are programs around which permit that,
if the radio outputs its AGC voltage or S meter data...and allow
you to spin the antenna while graphing the variations. I've done
this using another ham's signal (groundwave) as the source. I've
also done it, keeping the indicated signal strength at s9, and
using a calibrated attenuator on the RX. And, it's been done by
varying the signal source in a measured way, as well.
Each method has its own accuracy...derived from the AGC curve,
the calibrator, or the source power meter, depending on the method.
In AD1L's case, I recommended he arrange a safe way to continuously
monitor the AC line, while running the amp. That way, he can see
what's going on, and relate it to the Ep and Ip readings on the amp.
N2EA
Jim Jarvis, President
The Morse Group, LLC
We create high-performance organizations.
jimjarvis@themorsegroup.net
www.themorsegroup.net
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