[Laser] 5 mw laser transceiver kit

Tue Sep 21 17:49:14 EDT 2010

The Fresnels (20cm by 28 sm) are acrylic "magnifying sheets" bought at a
 five and dime store at $2 apiece. The secondary lenses, high diopter, 
are about $5 apiece from Surplus Shed. If Luxeon Rebels are used, add 
about another $8 for the LED. Add maybe $40 for electronics, most of 
which is the cost of the electrionics mounting boxes or DCB's. If you 
use PhlatLight LEDs, add about $30 for the LED, $5 for the BPW34 
photodiode and maybe $60 for the electronics. The PhlatLight also 
requires a computer CPU heatsink with fan - perhaps $5 at a secondhand 
computer fair. Piano hinges are used to fold the plywood Fresnel 
collimator mounting board down to its baseboard (add $20 for the 
plywood), and the tx Fresnel is separated from the rx Fresnel via a 
cloth "bellows" to permit the foldup. You could use a double layer of 
cloth-backed vinyl and black felt for that - maybe $10. Total of maybe 
$100, less if you have a junk box. The rest is carpentry, plywood, glue,
 screws, time and a photographic tripod for mounting.

Yes, I think this would make an excellent Scouting project - and without
 laser diodes, it's also a SAFE Scouting project. Mike VK7MJ has already
 led a construction project of a similar type for the Radio and 
Electronics Club of Southern Tasmania (REAST). In Australia, the usage 
of non-coherent light puts these units outside of the need for 
licensing, so you don't even need a ham "ticket" to operate them. And 
then there's the advantage that these binocular units work in full 
continuous duplex, like a telephone. The full duplex has obvious 
advantages for those wanting digital linking with a continuous return 
error correction path.

Yes, this will be a little bigger than a pocket sized unit. No, it will 
not be outrageously expensive or shipping-container-huge. I do believe 
that it would make a lot more sense to go with something having a better
 basis in atmospheric physics (and economy) than laser diodes, accurate 
glass optics and their severe power limits dictated by eye safety.

The pressure is currently on poor Clint, KA7OEI, who's preparing an 
article for publication on all of this, probably - in the initial 
instance - for QEX. Our group is currently building some trial fold-up 
units. And then, having crossed all of the "t's" and dotted all of the 
"i's", do we write a more popular construction article for a more 
popular magazine, like maybe QST or "Electronics World"?

One of the "snags" that we've hit is in the choice of flexible optical 
screening fabric to separate the tx part of the fold-up enlosure (Luxeon
 or PhlatLight enclosure) from the rx or photodiode part. The best 
fabric found so far is the stretchy stuff commonly supplied (ahem) as 
material for the manufacture of black fetish wear for sale through shops
 selling (ahem) 'interesting' videos and appliances in the seediest part
 of town. I'm starting to run out of the disguises (Groucho glasses, 
turned-up collar jackets and joke-shop teeth) that I need to wear on 
many purchasing expeditions, and my wife has begun to suspect my 
motives... If your Scouts can bear this tension, it will - indeed - make
 men out of them!

Chris (and Prue) Long, 2 Newton Street, Surrey Hills 3127, Victoria. 
Tel: +61 3 9890 8164.

http://www.modulatedlight.org

http://www.bluehaze.com.au/modlight/

http://www.modulatedlight.org/Dollars_vesus_Decibels_colour.pdf

================================================

> From: laser at codeadam.com
> To: laser at mailman.qth.net
> Date: Tue, 21 Sep 2010 17:27:24 -0400
> Subject: Re: [Laser] 5 mw laser transceiver kit
> 
> briefcase / Altoids tin
> 4 Amp/hr gel-cell / 2 AA batteries
> 
> Not even remotely the same....
> 
> ----- Original Message ----- 
> From: "Chris L" <vocalion1928 at hotmail.com>
> To: <laser at mailman.qth.net>
> Sent: Tuesday, September 21, 2010 4:56 PM
> Subject: Re: [Laser] 5 mw laser transceiver kit
> 
> 
> >
> > Our latest Fresnel/LED optical transceivers fold down to the size of a
> > briefcase, flat. With Luxeons thay can be powered off a single 4 Amp/hr
> > gel-cell. The optical units have a carry handle to a allow them to be
> > carried to mountain tops on foot. Where's the problem? --- Chris VK3AML.
> >
> >> From: laser at codeadam.com
> >> To: laser at mailman.qth.net
> >> Date: Tue, 21 Sep 2010 11:54:36 -0400
> >> Subject: Re: [Laser] 5 mw laser transceiver kit
> >>
> >> In reading backwards to the original post that started all of this, it
> >> appears to me that original intent of this project, "5 mw laser
> >> transceiver
> >> kit" was a small device that could fit in ones pocket, run off a couple
> >> of
> >> self contained small batteries such as AA or AAA (or even a 9 volt
> >> battery)
> >> and be able to demonstrate short range (couple of miles to a few tens of
> >> miles) optical freespace communications.
> >>
> >> I don't think anyone can argue that LEDs and fresnel lens are the way to
> >> go
> >> when it comes to ultimate DX but something of that magnitude and size
> >> hardly
> >> meets the goals of this project.
> >>
> >> If I knew nothing about this and saw a demonstration at a public meeting
> >> (such as a hamfest) where two people were talking over a light beam using
> >> equipment that was easily set up and when done could be slipped into my
> >> pocket I would be a lot more impressed than seeing a table full of large
> >> lens and batteries that needed to be hauled in a car or truck.  This in
> >> no
> >> way is meant to take away from the larger setup.  It's simply not the
> >> right
> >> tool for the topic being discussed.
> >>
> >> Now if the topic of this was "Ultimate DX freespace laser setup" then in
> >> my
> >> humble opinion the LED / fresnel setup would be the way to go.
> >>
> >> Of course in keeping with the original idea, "5 mw laser transceiver kit"
> >> there is absolutely no reason why one must use a laser.  It could be
> >> built
> >> using an LED or array of LEDS for the transmitter.  (Before the days of
> >> LEDS
> >> and lasers people used to modulate light bulbs!)   However, I think the
> >> laser is really the way to go for a small setup like this especially when
> >> it
> >> comes to public demonstrations and attacting new people to the hobby.
> >> The
> >> laser has self contained optics which are more than ample for this
> >> project
> >> and over the distances it is intended to be used scintillation is almost
> >> a
> >> non issue.  Many of us got our start using equipment such as this.  Some
> >> achieved their goal and went no further.  However, for others this simple
> >> setup wetted their appetite and eventually led to the "Ultimate DX
> >> freespace
> >> laser setup".
> >>
> >> I hope the concept of the "5 mw laser transceiver kit" does not stray so
> >> far
> >> from it's original intent that many will loose interest before it even
> >> gets
> >> started!!!  This topic has broken down into comparing apples and oranges.
> >> For many the "5 mw laser transceiver kit" is all the freespace optical
> >> communcation system they will ever need.  For those that need something a
> >> bit more, there will always be room for improvement later on and they
> >> will
> >> always have the "5 mw laser transceiver kit" as a reference to measure
> >> just
> >> how much better their "Ultimate DX freespace laser setup" is...
> >>
> >> Just my .02 1/2 cents worth...
> >>
> >> =====
> >>
> >> ----- Original Message ----- 
> >> From: "Tim Toast" <toasty256 at yahoo.com>
> >> To: <laser at mailman.qth.net>
> >> Sent: Monday, September 20, 2010 9:18 AM
> >> 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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