Re: circuit design to measure signal level variation ?


"Daniel" <dxmm@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:4419e888$0$17703$6d36acad@xxxxxxxxxxxxxxxxxxxxxxxx
Scott Kelley wrote:
Why are you fiddling with the output voltage? The AGC should provide a
pretty good representation, if logarithmic, of the signal strength. The
more signal --- the more AGC!

The AGC is not in effect at low signal levels. I will look into the
circuit to see what the possibilities are for increasing the gain so that
it is. Is that how signal level measurement is typically done?


The AGC line IS always in effect, even at low levels, because it is one of
the determining factors in the bias voltages of all the stages to which it
is applied. At very low signal levels, the AGC voltage may not vary
because the signal level, at the sample point, is too low to forward bias
the AGC diode, but there is still an AGC voltage applied to the previous
stages.

My point was that the measurement of AGC voltage alone will not allow me to
determine the signal level below the point at which the AGC circuit becomes
active.

How would this typically be dealt with?


Can you fiddle with the max4206 to make its o/p linear?

Don't understand the question.

You indicated that the o/p of the max4206 was logarithmic. Is it possible
to configure the IC so that its o/p is linear?

Oh, sorry . . . they call it a Logarithmic Amplifier, but the Max4206
converts a Log input to a linear output.


.

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