[Laser] Results form a crude signal to noise versus frequency check on my...

[Kerry Banke]

Last evening I had time to try the test suggested by Yves in the email 
below.  I set Spectrum Lab as he described and set the signal generator 
driving the LED source for a 5 dB signal to noise.  I  found the frequency 
response of my SFH-203 diode based receiver to still be  essentially flat 
from 10 Hz to 1000 Hz and down maybe 2 dB at 1300 Hz which is about  the 
high frequency limit for Spectrum Lab set up in this configuration. It 
appears that with this particular receiver setup, the operating frequency 
can be anywhere in the 10-1000 Hz range without significant change.
  - Kerry N6IZW -

At 07:57 AM 3/16/2006, you wrote:
>
>Very  good work Kerry,
>The  SFH-203 PIN diode ( 1 mm2, 11 pF) seems to give more  than about 1500 Hz
>bandwidth at -3 dB with your KGP  RX.
>If  you have time enough, try to make the same measurement with Spectrolab or
>  Spectran with only 0,042 Hz resolution by FFT point (less than 0,05  Hz).
>To  retrieve you 10 dB you will have certainly to reduce strongly the LED
>level.
>With  this very weak signal the photodiode current goes down and also its
>internal impedance.
>A  report will be very interesting.
>73  Yves.
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