[Laser] 5 mw laser transceiver kit

Tue Sep 21 11:54:36 EDT 2010

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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