[Laser] WB9AJZ laser RX problems

[n9jim-6]

Another possibility is that you are picking up weak 120Hz signals from 
nearby lights.
Try placiing the unit in a black box or cover with heavy cloth.
If it goes away its external "60Hz" lights.
This unit is VERY sensitive to such interference.

PS: all the other improvements mentioned are worth looking at too!

Jim
N9JIM/6
ex-WB9AJZ


Wendell Smith wrote:

>I built the transmitter/receiver from the web site of WB9AJZ/6:
>
>http://www.psnw.com/~n7stu/cheapo.html
>
>I am trying to get 4  units built up for roving during
>the January VHF contest, and these seemed to be rather
>simple. Here in Illinois the best DX is only going to be a
>few miles, unless you are fortunate to live in a Chicago
>hi-rise.
>
>There is a loud raspy buzz whenever the phototransistor is
>blocked.  Changing the 10Mohm resistance only changes the
>pitch.  Shining the 800 Hz laser produces a 800 Hz tone,
>but much weaker than the buzz.  Turned the laser TX off,
>and the buzz remained. Under normal room  incandescant
>lighting the buzz is gone, and the laser will still give the tone.
>
>I built a second unit, thinking that I had a bug somewhere,
>and the same result occured. Any thoughts or ideas for
>getting rid of the buzz, or any other hints for these circuits?
>
>Thanks,
>Wendell N9REP
>
>
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