‰ NOW 40 WPM ‰ SHOWN ON THE QST IN DEPTH WEB PAGE. IF YOU WISH TO USE THE RECEIVER ONLY ON THE HF BANDS BELOW 30 MHZ, YOU CAN DELETE THE SWITCH, WHICH DISCONNECTS THE UPCONVERTER FROM THE DONGLE AND REROUTS THE ANTENNA TO THE DONGLE AND SUPPLIES POWER TO THE OSCILLATOR. THE DONGLE REQUIRES NO EXTERNAL POWER OTHER THAN THAT SUPPLIED THROUGH THE USB CONNECTION. THE UPCONVERTER OSCILLATOR REQUIRES 5 V THAT IS SUPPLIED BY AN ONBOARD 78L05 REGULATOR FED BY A 9 TO 12 V DC SOURCE. A SERIES DIOD SDRSHARP. COM. THE COMPANY GRACIOUSLY PROVIDES THE SOFTWARE FREE OF CHARGE, AND ALSO SELLS THEIR VERSION OF A SOFTWARE DEFINED RADIO AS WELL AS OTHER PLUG INS TO ADD FEATURES SUCH AS SCANNING. THE LOWER FREQUENCY LIMIT OF THE DONGLE IS AROUND 24 TO 25 MHZ. THESE DONGLES WERE DESIGNED FOR TELEVISION AND COMMERCIAL FM RADIO RECEPTION. WHEN RE PURPOSED FOR HF HAM USE, AN UPCONVERTER IS NECESSARY TO ALLOW RECEPTION IN THE 1 KHZ TO 30 MHZ RANGE. MY UPCONVERTER CONTAINS JUST A FEW COMPONENTS AND IS VERY SIMPLE TO BUILD. IT CONVERTS THE BELOW 30 MHZ FREQUENCIES UP TO A RANGE THAT THE USB DONGLE CAN RECEIVE. THE SCHEMATIC SEE FIGURE 2 ILLUSTRATES THE SIMPLICITY OF THIS RECEIVER. COMBINE THE DONGLE, A SWITCH, SOME ANTENNA CONNECTORS, A MIXER AND OSCILLATOR, A POWER SOURCE FOR THE OSCILLATOR, AN LED, A FEW WIRES, AND AN ENCLOSURE, AND YOU HAVE A COMPLETE RECEIVER. ALL THE COMPLEX CIRCUITRY IS ALREADY BUILT INTO THE DONGLE, AND ALL ADJUSTMENTS ARE DONE VIA USERFRIENDLY SOFTWARE. THEORY OF OPERATION THE 100 MHZ OSCILLATOR Z2 GENERATES AN RF SIGNAL THAT FEEDS A DOUBLE BALANCED MIXER Z1. THIS MIXER CONVERTS THE BELOW 30 MHZ FREQUENCIES SUPPLIED BY AN ANTENNA THROUGH THE 35 ALL MODE 1 KHZ TO 1R7 GHZ SDR RECEIVER BUILD THIS SIMPLE AND VERSATILE HIGH PERFORMANCE RECEIVER FOR JUST A FEW DOLLARS. JAMES FORKIN, WA3TFS YOU CAN EASILY BUILD A HIGH PERFORMANCE MULTIMODE SOFTWARE DEFINED RADIO SDR RECEIVER. ALSO, YOU CAN BUILD IT FOR VERY LOW COST, AND HAVE A RECEIVER THAT TUNES FROM 1 KHZ TO ABOUT 1R7 GHZ IN TWO BAND SEGMENTS BELOW AND ABOVE 30 MHZ. THE HEART OF THE RECEIVER IS A WIDELY AVAILABLE USB DONGLE, SEEN IN FIGURE 1, ORIGINALLY INTENDED FOR TELEVISION RECEPTION. THE DONGLE IS AVAILABLE FOR 10 TO 15 ON THE INTERNET. ALTHOUGH THERE ARE SEVERAL VERSIONS OF DONGLES AVAILABLE, THE BEST ONE FOR THIS APPLICATION EMPLOYS THE R850T TUNER. THE ONLY CONNECTION TO YOUR COMPUTER IS VIA A USB EXTENSION CABLE THAT ATTACHES THE DONGLE TO YOUR COMPUTER. I INSTALLED TWO RF ANTENNA JACKS ONE FOR 1 KHZ TO 30 MHZ INPUT AND ONE FOR ABOVE 30 MHZ. THE 1 KHZ TO 30 MHZ ANTENNA INPUT IS ALWAYS CONNECTED THROUGH A LOW PASS FILTER AND AN UPCONVERTER CIRCUIT, AS SEEN IN FIGURE 2. IN THE LOW FREQUENCY POSITION, S1 ALSO ROUTES POWER TO THE UPCONVERTER. SELECT THE ABOVE 30 MHZ ANTENNA JACK WITH SWITCH S1. DONGLE SOFTWARE AND HARDWARE SEVERAL VERSIONS OF FREE SOFTWARE ARE AVAILABLE FOR DOWNLOAD FROM THE INTERNET. I USE SDR SDRSHARP WITH MY RECEIVER. YOU CAN DOWNLOAD AND LEARN ALL THATS NECESSARY TO INSTALL AND CONFIGURE THE SOFTWARE AT WWW. ‰ END OF 40 WPM TEXT ‰ QST DE W1AW ƒ