[Laser] led txr

[John Randall]

Hi Stuart, Still feeling my way around laser comms and baseband usuage. I have 
yet to try it over any considerable distance, other than across the front 
room....hi. There is a field nearby which has a bit of space, so might go an 
play there one evening. I would have to use a mirror on the opposite end to get 
the beam back to the detector. Should be fun trying to set it up.
Nice one on the distance you achieved. I also found the aussie laser reflector, 
so that will make more interesting reading.hi

73
John



________________________________
From: I <stuart.wisher at talktalk.net>
To: laser at mailman.qth.net
Sent: Thu, 4 November, 2010 15:17:14
Subject: [Laser] led txr


John,



we use lenses (100mm glass, or A4 size fresnel) to focus the beam here, so the 
lensed products may be more intense, but not effectively brighter when focussed. 
Our signals, FM or SSB go out on a 25kHz or so sub-carrier, so we need a high 
speed detector. I am still amazed an ldr works at all. A laser might be fine at 
short range, but you try aiming it at distance, I have done it at 15km, nearly, 
but not quite impossible. Even aiming the led is difficult with its effective 
one tenth of a degree beamwidth (calculated and confirmed by measurement).


By the way, we were out again last night and successfully completed a 65km 
contact between me, G8CYW and G8KPD/G8PNN. Signals were still end-stopping on FM 
and SSB. We could even continue when the signal disappeared to the naked eye 
when mist formed, we held the link for about an hour.


Stuart, G8CYW
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