[Laser] 5 mw laser transceiver kit

Tue Sep 21 05:42:55 EDT 2010

Hi Chris
"...why do people persist with lasers for atmospheric optical ommunication"

It is because the very small TX and focusing device, the low power PSU needed, the ultra high speed capability, the nearly perfectly monochromatic produced light that allows ultra narrow optical filters and so the by day opérations capability...
These DX experiments are not possible with LEDs today over a few miles:

http://home.arcor.de/w_fritz/Laser/Harz.html
http://home.arcor.de/W_Fritz/Laser/Harz1.html
http://home.arcor.de/w_fritz/Laser/Harz2.html

73
Yves F1AVY
http://f1avyopto.wifeo.com

--- En date de : Mar 21.9.10, Chris L <vocalion1928 at hotmail.com> a écrit :

> De: Chris L <vocalion1928 at hotmail.com>
> Objet: Re: [Laser] 5 mw laser transceiver kit
> À: laser at mailman.qth.net
> Date: Mardi 21 septembre 2010, 4h19
> 
> I have just one question.
> 
> When atmospheric physics dictates that spatial coherence
> (ie laser light) is a hindrance to scintillation-free
> communications; when the reliability, ruggedness, safety,
> cheapness, and measurements taken on the validity of
> LED-Fresnel combination are proven by a series of world DX
> records in Australia and America; when ARRL rules have been
> changed changed to suit those measured results; while lasers
> are costly devices demanding even more costly collimating
> optics, and when many governments are imposing bans on the
> outdoor usage of laser pointer devices...
> 
> ...why do people persist with lasers for atmospheric
> optical communication?
> 
> Chris Long, VK3AML, 2 Newton Street, Surrey Hills 3127,
> Victoria. 
> Tel: 9890 8164.
> 
> http://www.modulatedlight.org
> 
> http://www.bluehaze.com.au/modlight/
> 
> http://www.cylindersontheweb.angelcities.com
> 
> http://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf
> 
> 
> =============================================
> 
> > Date: Mon, 20 Sep 2010 06:18:22 -0700
> > From: toasty256 at yahoo.com
> > To: laser at mailman.qth.net
> > Subject: [Laser] 5 mw laser transceiver kit
> > 
> > Hi All
> > 
> > It's great to see someone has put a kit together. That
> is sure to 
> > spark some interest in optical coms. In the interest
> of a little 
> > fun competition, it would be nice to have a simple kit
> for laser 
> > com's too. One obvious advantage (or not so obvious)
> for laser 
> > over LED, is size and power consumption. A simple
> laser transceiver
> > could be made very small and portable, even
> pocket-sized and 
> > battery powered. Under 90 ma. for most 5 mw diodes.
> > 
> > It would help if everyone could start with the same
> size, easy to
> > obtain, enclosure. One that comes to mind is the old
> "Tuna Tin 2" 
> > kits. You could actually use a tuna can (Tuna Tin THZ
> or 
> > Tetrazzini?) but someone suggested to me to use one of
> those 
> > "Altoids" candy tins. They have an easy access door
> and complete
> > sheilding, plus plenty of room for a circuit board and
> batteries
> > inside. These are the large 5" x 3" x 1" inch size
> boxes. They 
> > also come in a couple smaller sizes and even round
> ones, all with
> > resealable metal lids or doors.
> > 
> > I was looking at some amplifier circuits today and saw
> this high 
> > gain hearing-aid design that uses 3 transistors and
> one battery 
> > (1.5v). If you switch the microphone with a photo
> detector front 
> > end, you have a high-gain receiver plus part of the
> transmitter 
> > too. A laser transceiver could be made very small and
> energy 
> > efficient using a low voltage like 3 volts (2 cells).
> A 3, 6 or 
> > 9 volt design for the small light-weight battery
> sizes. With a 
> > dual 555 timer chip, you can have a simple high
> quality PWM AM 
> > for the laser and a tone generator for MCW or
> alignment. The 
> > goals being low cost, light wieght, easy to put
> together etc..
> > 
> > Relatively cheap optics that work well:
> > If you are willing to take apart some junk equipment
> you can find 
> > lots of optical goodies. The old VHS Camcorders can
> supply most of 
> > the optical parts. An old DVD player will get you a 5
> milliwat red
> > laser diode (these are often dual wavelength
> visible/IR diodes with
> > three pins, or four pins if it has a monitor diode)
> and some small
> > lenses to use. These even have one lens you can use to
> collimate 
> > the laser fairly well (the laser pickup "output" lens
> is a 5mm or 
> > 6mm f0.9 or faster type) or it can adapt the beam for
> use with a 
> > larger lens. The main large glass lens on the
> camcorder is usually 
> > a 25 to 50mm f1.0 type when used by itself. It can
> work for either
> > transmitter or receiver. Some of the older ones have a
> fine 
> > adjustment twist focus. 
> > For short range use, it might be nice to be able to
> defocus the
> > transmitter and receiver some - up to 10 degrees or
> more maybe - 
> > these twist focusing lenses would be great for that. 
> > Inside the camera zoom lens are a few smaller glass
> lenses in both 
> > positive and negative types plus a special "eyepeice"
> type assembly 
> > - similar to a 15 - 20mm Kellner telescope eyepiece.
> This could 
> > make a nice finder when paired with a larger objective
> lens and a 
> > cross-hair. The video viewfinder eyepiece is also
> adjustable and 
> > could be used for either one or a finder. It is
> usually a 20mm F1 
> > or F2 plano convex plastic lens. 
> > The performance won't be excellent obviously with
> these small 
> > lenses but should work for the shorter ranges ok.
> (under 50 miles 
> > or so?? :) you can always break out the big optics for
> better 
> > performance.
> > 
> > 
> > tim toast
> > 
> > 
> > 
> > 
> > 
> > 
> >       
> >
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