The transverter is pretty straightforward, but the led transceiver (now heard signals out to
46km, and had a full FM and SSB QSO at 25km straight through 20km plus of city lights and
stadium floodlights) needs some surgery on the Osram golden dragon red led type LR W5SM-HYJY-1
to remove the protection diode so you can reverse bias it (simply cut through the lead to the
protection diode, your multimeter on the diode range will tell you when you have done it) . I use
43V reverse bias, but another sample needed 48V so it is an adjust-on-test issue.
The rx front end for the transverter is just the same as in the led transceiver head minus the
relay and switching, a pretty recognisable variant of the KA7OEI design. This design also shows
how to connect a separate LED to the transmit port of the transverter, ie, in series with an
8.2 ohm 3W resistor, use the lower value at your own risk. I use some very thin fiberglass pcb
to mount the LED on to a heatsink (die cast Al box), take care to keep the capacitance to 0V as
low as possible especially if using the LED as a receiver. Originally, the transverter used
separate rx and tx heads as described, but the led transceiver head does both jobs and only
needs a single optic. An IRF 540 is an equivalent for the MOSFET driver, adjust the pot for
100mA standing current through the LED, (start with the pot at 0V) this will peak up when on
transmit to 0.5A average or higher with the lower value resistor.
Stuart G8CYW
|
|
