6 Jan 2012

Optical receiver head completed

481THz optical receiver with 100mm lens
I now have a 100mm lens set-up in some grey drainpipe with 4x sighting scope attached on a tripod together with a "simplified version 3" KA7OEI head (of sorts) with a BPW34 detector. In my version the cascode stage is just followed by a single common emitter stage driving a crystal earpiece, although I intend to add an emitter follower so I can connect to my PC (to use with Spectran/SDR) or a transverter.

A 5mm 20 degree red LEDusing just its own built-in lens was shone out of the stairway window aiming down the street in daylight with 1kHz modulation. It was taking around 20mA. I then walked with the kit to the far end of the street and the signal was solid (S9) in the RX earpiece at a distance of about 0.25km. I now need to find a more distant test range and see how far this can achieve. Depending on results I hope to go looking for GB3CAM next week.


Anonymous said...

You could do optical SETI with that gear as well, Roger!!

Tony B

Ivan Savov said...

Very nice construction!
I am an information theorists, but today I am researching practical optical encodings/decoding and your pic popped up on google images.

Can you tell me a bit (or point me to docs) what kind of data you can send to this? Can you send AND receive with the same optics?
And at the same time (full-duplex) ?

Is it light pulses or AM or FM or something?

I am wondering about what cool things one could do with this + a polarization filters at the sender
and at the receiver.

Also, I would like to use your picture in my PhD thesis, as an illustration of a multiple access channel -- imagine that there are senders pointed exactly at your receiver.

Would you mind if I include that picture?

My email is first dot last at gmail dot come