Progress on the new 481THz beacon TX

Today I made a start on the new optical QRSS3 beacon. This time, the circuit has some improvements: a continuous sub-carrier option and a choice of audio subcarrier frequency. Also, the frequencies are now derived from an HF crystal so stability will be excellent.

The part completed new 481THz QRSS3 beacon

The oscillator/divider is a 4060 IC and this is enabled by the output of a K1EL keyer IC programmed to send "XBM" in QRSS3.  The square wave output from the 4060 feeds the gate of an IRF510 FET which switches the 280000mcd, 10mm diameter, LED in 100mm optics.

A possible refinement will be to pull the crystal using the keyer output signal so that I have a continuous carrier but FSK keyed. This would mean I'd always have a signal to aim at, but with FSK QRSS3 CW on it. I'm not sure how much pull I'd get after dividing down if I just changed one of the capacitors loading the crystal. I shall have to experiment and see. Even as little as 5Hz would be enough, but that would need 50kHz shift at crystal frequency! A better way may be to key the frequency out of the 4060, so mark is, say 550Hz and space 1100Hz or vice versa. Plenty to try tomorrow.

Simpler 481THz beacon TX

This afternoon I built a simpler CW/QRSS3 beacon for lightbeam experiments. Rather than use a crystal divided down in a 4060 IC I simply used my K1EL keyer IC's sidetone output to drive an IRF640 which drives the 1W LED. 10wpm CW or QRSS3 beacon message is therefore produced on an 800Hz subcarrier. The stability of the sidetone from the PIC keyer is quite sufficient for QRSS3 although not good enough for QRSS30 or 60.

Simple beacon keyer IC: the K-ID2

Looking around for a simple beacon keyer to use with a QRSS beacon, I discovered the ICs sold for $6 (available via Paypal) from K1EL. This 8 pin IC looks ideal as it allows a variety of pre-programmed messages to be selected and sent at predetermined keying speeds.

See http://k1el.tripod.com/KID.html . At $6 each you can hardly go wrong with this. I shall be ordering a few shortly.