[Laser] Initial 650 nm tests

[Jim Moss]

Way to go!

So that's a 1.4KM path! And those reflectors aren't all that great. They really
spread the signal a fair amount.  With a good RX you will be able to hear your
signal off "non-reflective" surfaces too.

For testing I use a tree about 2KM away, with a on/off keyed laser (1KHz) and
30mW IR can hear the signal bounce off the different areas of the leaves (AM
noise).

Good luck!

Jim
N9JIM

--- Leigh Rainbird <vk2krr at bigpond.com> wrote:
> Built my AM 650nm transceiver today.
> 
> Have been mucking around with the acutal laser module and haveing a
> bit of trouble focusing the beam. Its a pointer I modified.
> 
> I have some bicycle reflectors nailed to the trees down the front
> paddock, around 0.8 Km away. I aimed the beam at the reflectors and
> could see it coming back.
> 
> I went down the front with the RX section and tried to see if I could
> hear audio coming through, but the beam was not focused enough at
> that distance.
> 
> Tried a slight refocus and went back down the front, but when I got
> there the beam moved to high and I could not access it.
> 
> Moved the beam closer to ground and drove down there again and found
> it on the ground. I came back to about 0.7 Km and tried to see if I
> could copy any audio. The beam was not to bad at that distance this
> time, probably about 1/2 meter diameter. No copy initially then I
> realised the RX antenna was not in the beam fully, after I got fairly
> well in the center I could hear audio out the speaker!! wow!
> 
> Q5 copy of a playback of the VK6 openings from last year, amazing to
> copy audio from a laser beam of light. I was using only the small
> photo-diode.
> 
> Well, i've set the mark and now I'll have to try and better the
> distance. Will be interesting to see how far we can go.
> 
> Regards
> 
> Leigh VK2KRR
> 
> PS- This is an Oatley Electronics kit
> 
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