[Laser] NO RX XE2AT

[Art]

At 06:15 PM 2/10/04, you wrote:

>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
>

Hi Bob,

James, N5GUI sent me the receiver schematic. I asked him to send the=20
transmitter schematic too. Thanks for the offer, but I think I'll have both=
=20
schematics soon.

It looks like Ramsey never intended these to go more than a mile and only=20
then for demo purposes. I agree that it should be easy to hook up something=
=20
alot better than the stock phototransistor. With much higher sensitivity,=20
shielding might be necessary however.

Looks like a shoe in for a simple photodiode substitution and some changes=
=20
to U1 (so it does the current to voltage conversion).

I'll write some more after I get the schematic of the transmitter from=
 James.

Art





>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
> > >
> > >_________________________________________________________________
> > >Charla con tus amigos en l=EDnea mediante MSN Messenger:
> > >http://messenger.microsoft.com/es
> > >
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