[Laser] led txr success

[stuart.wisher at talktalk.net]

Dear all,
Mk2 led transverter has now been field tested at the weekend. The result was a full QSO From G8CYW to G8KPD across northern England, a distance of 46km during an optical comms night involving five stations at various locations. Signals on the transceiver on both SSB and FM were limiting the driver, an FT817. I also received a strength 7-8 SSB signal over 66km from a station in north yorkshire using the "wrong" kind of led, a batwing emitter with a large radiating area which illuminated a 1km dia patch at my end (instead of the 200m we achieve with golden dragons leds). The lens used was a 100mm dia magnifying glass in a plumbing tube, but I also have an A4 sized Fresnel lens system for when this stuff starts getting difficult.


We are going out again soon to have a proper QSO over 65km or so, and try for an 82km contact, which if made, would I think make a new UK record, certainly for leds rather than lasers.


Mk2 consists of a RC coupled version of Clints simplified receiver with no low pass filtering, a relay to switch the led from forward bias on transmit to reverse bias on receive, with 43V from a stack of keyfob batteries and button cells. The led requires some "microsurgery" to remove the wire to the protection diode. It makes as good a photo diode as the purpose built SFH2030 we were using in a separate rx/tx system.


Regards to all


Stuart G8CYW