[Laser] Ramsey Kit Modes

[Les Rayburn]

Art,

Thank you for the reply. Glad to hear that others share my "slightly" more modest goals for laser communications. I've also thought about using this during a contest for some additional bonus points. 

Can you supply me with a link or perhaps copies of the documents themselves for your suggested modifications to the Ramsey receiver? 

73,

Les Rayburn, N1LF
EM63nf
121 Mayfair Park
Maylene, AL 35114



From: Art 
Sent: Monday, February 16, 2009 11:55 PM
To: Les Rayburn ; Free Space LASER Communications 
Subject: Re: [Laser] Ramsey Kit Modes


Hi Les,

My longest 2 way QSO has been 50 feet, made at a M/M VHF contest site in the 90's. I've done lots of listening and lots of sending, but only one way attempts. For the purposes of the contest, we only need equipment capable of working 1 kM or so, which can be done with a phototransistor (no other optics needed), and LM741 rx with any laser (1 milliwatt is fine) used in conjunction with a chopper (fan), keyed CW with the hand in front of the beam. The laser we used was a very tired 1 milliwatt tube that had a less than optimum 3 millirad divergence. This setup has been tested by me and my wife at 1 mile. 

Eventually, I'd like to make VUCC from Mount Washington, NH during the same UHF contest. 

I DO NOT share your optimism regarding the suitability of the PGP front end with the Ramsey system. Basically, the Ramsey system needs a 12 KHz receiver bandwidth in order to pass the pulses that come from the distant transmitter. With the PGP front end, you will peak in the 20 Hz to 100 Hz range, depending on the type of photodiode you use.

I documented a proper bandwidth receiver modification for the Ramsey using an OPT0101, which were very cheap and easy to use (1 resistor sets the receiver bandwidth, 8 pin DIP, diode and op amp in the same package), although they are a little noisy by some standards.

Regards,

Art


  James,
   
  Took your advice and searched the archives for the postings regarding the Ramsey Kit and the XE2 attempt (successful) at VUCC. It appears that the K3PGP "front end" installed on the Ramsey kit might be a good modification to start with. 
   
  I saw a lot of your posts, but none of the ones I read indicated how much you'd experimented with long distance work. One critical difference between the XE and our attempts is that we've identified a convergence spot that has easy QSO's with four grids (all within 2KM) and good LOS to a distant fifth grid. Our real effort will be making that long distance QSO. The first four grids should come easily. 
   
  Please share with me your thoughts on this approach and others that I should possibly consider. Thanks again!
   
  73,
   
  Les Rayburn, N1LF
   
   
   
  Les Rayburn, director
  High Noon Film
  100 Centerview Drive Suite 111
  Birmingham, AL 35216-3748 
  205.824.8930
  205.824.8960 fax
  205.253.4867 cell
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