[Laser] 5mw laser tranceiver kit

[n5gui at cox.net]

Tim and Tom

An interesting schematic.

What I see is the need for the microphone and the photodiode to be "matched" in their characteristics.  Otherwise one, and I presume it would be the photodiode, will not have enough system gain.  I suppose that it might be of practical use if you load down the microphone element so that at the amount of gain needed by the photodiode, it does not overdrive the amp.

Likewise on the output, the LED and the 8 ohm earphone ( or speaker, or other load ) would need to match.

If the thought is to drop in a LASER, the problem on output becomes even tougher.  LEDs are pretty linear current to light conversion devices, but LASERs are not.  

That is not to say that I see anything that is fundamentally wrong with the circuit.  A commercial device might well be simplified to that point minimized part count or otherwise optimize the design.

I think that if I tried to design a practical prototype using that schematic, I would probably go nuts trying to balance both inputs and outputs.  Not that I would have far to travel, or much skill at the task.

James
 n5gui



---- Tom Becker <GTBecker at RighTime.com> wrote: 
>   > ... http://www.aladal.net/toast/5mwkit1.jpg
> 
> Tim, I looked at your schematic and was struck by the irony that the 
> transmitting diode could be either a laser pointer - or an LED.  Maybe 
> Chris would be happy to see a DP3T switch on the kit - to demonstrate 
> the advantage and disadvantage of each radiator - and, perhaps even 
> different receive diodes.
> 
> How is this different from my second CW transmitter, a Heath DX-20 (the 
> first was a homebrew hand-wound 6V6 pine-chassis, from the '56 ARRL 
> Handbook, I think), which offered five-band switching?  I learned 
> quickly that 15 meters, at the time, did not work as well as 40 did, and 
> 80 was cluttered with summertime QRN.  I learned that advantage by 
> myself, given the opportunity to try both.
> 
> Tom
> http://www.ustream.tv/channel/bowcam
> http://www.ustream.tv/channel/cape-coral-marine-radio VHF
> http://67.207.143.181/vlf9.m3u VLF
> 
> 
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