Have a look at this: http://www.opticalantennasolutions.com/ Claims they are 100 times more sensitive than any other device. ----- Original Message ----- From: "Art" To: Sent: Sunday, March 14, 2004 12:51 AM Subject: Re: [EE]: Long-Range, Low-Power IR Transceiver > Read all your questions. > > We currently have stations working each other over a 22 mile line of sight > path with LED transmitters. > > Forget building a photodiode/op amp receiver. You can buy top of the line > Burr-Brown opt-301 ($16, comes in a shielded can package) or BurrBrown > opt-101's ( $6. same electronics, but unshielded DIP package). If you are > interested in the opt101 unit, it's being sold for $2.50 each at this > moment. These Burr Brown units are very very hot receivers and include the > op amp and photodiode in the same package. They draw 120 microamps from a 5 > volt supply, so there's alot of sensitivity available for low $$! > > For less than optimum sensitivity requirements, TAOS has a whole line of > optical receivers (photodiode/amp assy) in the same package-their prices > are $3 to $2.50 each. Taos sends free 'samples'. > > Are you a member of the of the laser communications email list??? These > guys do many different modes and have good general knowledge of lightwave > transmitters and receivers. They are mostly ham radio operators, but there > is no licensing requirement on the lightwave bands, so the list is open to > all who have an interest in lightwave communication. > > For serious distance, use an 8 by 10 fresnel lens (commonly called a page > magnifier), available for 6 bucks at you local office supply or stationary > store. > > My interest is in extremely weak non line of sight troposcatter > communications (also known as over the horizon communications by the > military). For this, photomultiplier tubes, big light collectors and > optical passband filters are required and the rates are 1 to 3 bits per > hour using .001 Hz bandwidth receivers (DSP soundcard/PC with good > software). Others in the group do high speed digital modes, still others do > carrier modulated studio quality audio transmissions. > > If I can help further, send me a message off list. > > Art > > At 09:37 AM 3/13/04, you wrote: > >Hi all, > >I'd like to build myself a Long-Range, Low-Power IR Transceiver. > >I know that the "long range" and "low power" may seem contraddictory, > >but I thought, if I produce a very intense but very brief IR "flash", > >the flash may be visible at a long distance, yet the average power > >will be low. Rather than emitting 30mW for 5mS, I could emit 3000mW > >for 50uS, with the same average power, but the intensity would be 100 > >times higher (and the range, IIRC, 10 times longer). > >I intend to encode data by time-modulating these pulses, e.g. at a 1mS > >rate transmit both clock and data (one clock and one data bit/pulse, in > >sequence, continuosly.. clock pulse always present, data pulse present > >if "1" and absent if "0"). > >The receiver would filter out DC, through a high-pass filter to detect > >almost only those very brief pulses, and nothing else. > > > >Does my design makes sense? > > > >I'm now on the component identification phase. I examined the datasheets > >of all the IR LEDs and photodioes/phototransistors that my favourite > >online shop sells (small shop but excellent service and prices), and I > >selected these devices: > > > >tx: > >TSHA6203 (875nM) > >TSIP5201 (950nM) > > > >rx: > >BPW83 (875nM and 950nM) > > > >The other devices I examined in detail were: > >BPW21, BPW34, BPW40, BPW41, BPW42, BPW77N, TSTS7103 > > > >But I'd have some questions for you: > > > >1) All the rest being equal, what wavelength is preferable, 875nM or > > 950nM? I know that 875 would be better if there're glasses inbetween, > > but my application will be mostly free air. > >2) What is in general preferable on the receiver side: photodiode or > > phototransistor? Why? > >3) Do you have any better LED and photodiode/phototransistor to advice > > than the ones I selected? I'd have no problems to buy those from > > another shop.. if it's worth the extra shipping charge, etc.. of > > course (i.e. I'd have to make two orders instead of one). > >4) How does the world look like, at those wavelengths? Is it generally > > "dark", or at 875-950nM reflections and absorbtions from objects is > > more or less like visible light? > >5) At such high pulse currents, should I fear damage to my eyes if I > > accidentally look into the (invisible) beam? > >6) To increase further the range, I'm thinking about making a 2m long > > tube, internally reflective (aluminium foil), diameter slightly more > > than the IR LED. This should decrease the angle of emission, but also > > make it more powerful and concentrated, right? (i.e. a bit like a > > poors' wannabe laser). > > For the receiver I'm thinking about using a small telescope, pointing > > it to the transmitter (hopefully 1+ Km away.. ehm). Will the lens be > > transparent for the incoming 875nM or 950nM light? > > > >Thanks! > >Andrea > > > >-- > >http://www.piclist.com hint: The list server can filter out subtopics > >(like ads or off topics) for you. See http://www.piclist.com/#topics > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.