[Laser] New RX

[Tim Toast]

hi Yves
That looks like a good design. I like how you can switch between the two modes easily. It's about that time of year again when the moon is high in the sky between new moon and first quarter phase. It is also near perigee at those times. Have you tried out those Zeiss tank mirrors yet?

http://www.aladal.net/toast/moon.html


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Hello all.
You will find at:
http://sd-1.archive-host.com/membres/images/22679775843705539/UltimateRX6.jpg
... my new charge amplifier photodetector for low rate optical pulses in astronomy or pulsed laser cloud bounce.
This receiver uses the Miller capacitance of the 2N4117 FET as feedback integrator.
This device can extract very short and weak pulses from a low frequency background (scintillation) if their rate is lower about one hundred by second.
With the second FET fitted in cascode, the response becomes linear with a bandwidth better the K3PGP classical schematic and can reach over the kilohertz with a very good sensitivity.
The specified FETs types are mandatory and some resistors values can be adjusted to centre the static output voltage point at PSU/2.
Of course the cooling (without moisture!) of the first FET 2N4117 and the S5973 photodiode improuves again the sensitivity.
73 Yves F1AVY
http://f1avyopto.wifeo.com