[Laser] Reasonable Sensitivity Checks ?

[steve kavanagh]

I finally got back to working on my laser gear and now
have a basic receiver going (60mm lens, unbiased
CD-player detector capacitor-coupled to high-impedance
MPF102-2N5088 preamp, followed by half a TL072 and an
LM380N-8 feeding headphones).  Audio bandwidth is
about 1 kHz at -3 dB points with peak response near
500 Hz (down nearly 10 dB from the peak response at
120 Hz, in theory).

Are there any simple tests to check for reasonable
sensitivity ?  I am not, at this stage, looking for
the ultimate in performance...just something to get
started with.

So far I have observed that I can tell the difference
in noise level between pointing out the window at a
cloudy daytime sky and pointing into the room (room
lights off).  However, this difference is not huge,
and the receiver does not saturate on the daytime
cloudy sky noise (keep in mind that due to the
capacitive coupling it can not saturate due to DC
levels alone).  I have been able to detect
streetlights at night at up to about 500m distance and
a radio tower strobe light in the daytime at around 5
km (gives just a popping sound in the headphones).

Can anyone comment from their own experience on
whether this sounds reasonable ?

Steve VE3SMA


	

	
		
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