[Laser] NO RX XE2AT

[laser@mailman.qth.net]

Hi Art


Unless someone else sends you something
I will scan in the Ckts and send them to you
As the diode det is cap coupled into the rcv I would think
any other detector ckt ,, with proper BW should work
I can see the IF signal at 14 Khz in an LF rcv . There are many
other outputs from this Ramsey rcv but 14 Khz at the time appeared
to be the loudest

The signal was stable enough th copy OK using a Audio analyzing program
( Argo ) at a speed of 60 second dots ,, it is relative drift free

Bob  K3DJC




On Tue, 10 Feb 2004 15:03:34 -0500 Art <artky1k@uninets.net> writes:
> Hi Al,
> 
> I have a more basic question....
> 
> You report both QSO partners could see each others beam.........  
> But, you 
> only comment on your receiving attempt and what you saw from your 
> end of 
> the path.
> 
> I wonder if you can give more details please.
> 
> Both stations were able to see each others laser???
> 
> Both stations were unable to hear the others signal, or was there 
> only one 
> attempt to receive?
> 
> If both stations were attempting to receive, did both stations use a 
> 4 inch 
> lens???
> 
> ------------------------------------
> 
> My guess would be that the Ramsey transceivers aren't quite up to 
> the task 
> of distances that great. They use a carrier to send the information 
> on, so 
> your receiver has to be responsive at the carrier frequency-which 
> means you 
> give up a VERY LARGE degree of sensitivity due to this overhead.
> 
> The noise is proportional to the square of the relative bandwidth. 
> Since 
> your receiver has to be sensitive to the carrier frequency (which I 
> think 
> was 30 KHz), you have a greatly reduced ability to copy weak 
> signals.
> 
> Comparing 2 identical systems, one receiving at 30 Khz and the other 
> at 1 
> Khz.... The transmitter for the 30 Khz link would have to be 900 
> times 
> stronger to give the same quality of reception.
> 
> I think your results would be very much different if you used a 
> shielded 
> Burr Brown opt101 receiver chip with the bandwidth set to 1 Khz by 
> the 
> external feedback resistor. Your transmitter would be switched at 
> (about) 1 
> Khz, and it's a much simpler circuit. This would send a tone only, 
> unless 
> you modulated the laser with audio from a microphone.
> 
> ------------------------------------
> 
> You did not hear any interference from the city lights because your 
> carrier 
> frequency was far removed from the 50 or 60 Hz noise emitted by the 
> city light.
> 
> You probably did not overload the photodiode itself, they have 
> incredible 
>  range! It is possible that you overloaded the receiver electronics 
> though. I don't have a schematic for these Ramsey units. But you can 
> 
> improve the receivers electronics rejection of  50/60 Hz overload by 
> using 
> appropriately sized coupling cap. You want to insure that the 
> receiver 
> carrier can pass from the photodiode to teh receiver without much 
> attenuation, but the 50/60 Hz must be attenuated.
> 
> Does anyone have a schematic of these units??
> 
> Art
> 
> 
> 
> 
> At 09:10 AM 2/10/04, you wrote:
> >Hi boys yesterday we make some test at 20 miles and after 2 hours 
> we can 
> >saw the both sides of lasers !! was a great experience but NO 
> reception 
> >!!!! I can see a lot of city lights but no noise beaming the 
> receiver to 
> >lights, I am using a 4 inches lens and the Ramsey Electronic Kit.
> >The Laser was very strong but I think is the LED on the receiver, 
> What I 
> >can do ?
> >73 de Al
> >XE2AT
> >
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