Will take a look at URL:
http://www.ac6v.com/sunit.htm


Maybe the National Semiconductor NE604 IF amplifier IC would be worth
looking into. Claims say it provides an accurate signal strength logarithmic
output that closely tracks the input signal level over a wide dynamic range
that could possibly be used for driving an S meter circuit.

--
CL -- I doubt, therefore I might be !


"Will" wrote in message
...
I was wondering how commercial equipment go about calibrating the S meter
and whats the best way of building a calibrated S meter that would be
reliable as a professional field strength meter?

Since most S meters just read AGC voltage and it would be easy to build
some interface with a CPU to read voltages and calibrate this way. The
question is this, is a S meter calibrated this way actually reading in a
accurate way whats occurring at the antennas terminal. Since most antenna
inputs are not 50 ohms J0, how would you design a system like a spectrum
analyzer that measures signal voltage at the antenna terminal?. I would be
interested in some ideas, i am homebrewing a shortwave receiver however i
wanted a calibrated S meter in Dbuv, Dbm, S units and Millivolts. I also
want to use a calibrated antenna for a Antenna factor input to have a
meaningful long term view of propagation signal strength.

Thanks
Will

"Caveat Lector" wrote in message
news:64Gcg.177511$bm6.76448@fed1read04...
Will take a look at URL:
http://www.ac6v.com/sunit.htm


Maybe the National Semiconductor NE604 IF amplifier IC would be worth
looking into. Claims say it provides an accurate signal strength
logarithmic
output that closely tracks the input signal level over a wide dynamic
range
that could possibly be used for driving an S meter circuit.

--
CL -- I doubt, therefore I might be !


This is ok, but the one thing is that any Signal strength IC like the 604
has a constant slope and the S-Meter will be rather compressed in the 0-9
s-units range compared to the over S9 range (obviously fixable with meter
scale). I don't recall the 604's dynamic range. You could make a two slope
correction above S9, but I'd have to do some scratch paper work to figure
out the circuit [ probably as simple as a resister and diode in the right
place]. Or use two of them and change the gain into one to get the
different slope. I don't recall the 604's dynamic range. I have some
SLx16...oops can't remember the numbers (? 1316?... 1613? ) , that are
cascaded for large dynamic range log amps.

Just some ideas.

73, Steve, K9DCI