Ran another linearity test this time from 60mHz to 500mHz.
Power level was set at -70dbm and -30dBm.
Two conditions for each power level. Compensation components
in circuit and components bypassed.
Results were pretty interesting for the bypassed assessment. It was
about a 160mv drop, which would represent about a 6dBm loss, over a 50mHz span
and 205mv over the entire range.
Since I soldered in a jumper in order to bypass the
compensation components, I wonder if it is having the effect that is
responsible for the rapid falloff. I suppose
I could put in another jumper of a different size/shape and see if there is any
change in the curve. Even though I’m not all that interested in in frequencies
this high, the curiosity factor alone is enough to try it. Besides the whole idea of these experiments
is to learn all I can about this device first hand.
The compensated response shows a 94mv drop over the range
from 60mHz to 500mHz. That would be
close to a 4dBm drop. Not too bad and certainly can be easily taken into
account either by software or a “cheat sheet”.
As well I injected various hf frequencies into the Arduino
input along with the 8307 output. I used a .1 cap to isolate the signal
generator. Long story short here was, unless you inject a signal at the level
of 0 to 5 dBm, there was no effect on the readings of the dvm. Even then it was only 1 or 2mv. However the important thing here was not how
the dc output was performing but how the Arduino behaved to any harmonics that
may bleed through and get into the adc. The readings being displayed by the
Arduino were steady and never once changed values no matter the frequency or
power level. So for me the debate begins on how necessary is the lpf in that
path?
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