‰  NOW 40 WPM  ‰  TEXT IS FROM JULY 2012 QST  PAGE 38‰
OF THE MIXER TO PROTECT THE GILBERT CELL FROM CROSS MODULATION.  THIS
CONVERTER WORKS WITH ANY RADIO USING A 455 KHZ IF SYSTEM THAT PROVIDES A 1
TO 20 MV SIGNAL FOR A S 9 METER READING AT THE OPTIONAL FILTER PORT.  THE
SECOND OP AMP IN THE TL072 PACKAGE IS USED TO PROVIDE A 7 KHZ HIGH PASS
FILTER.  THIS FILTER CAN BE BYPASSED IF REQUIRED.  PCB AND IMPLEMENTATION
THE PROTOTYPE OF THIS CONVERTER WAS BUILT FOR USE IN THE YAESU FT 817, BUT
NOW A LOT OF AMATEURS HAVE BUILT THE LIF

RADIOS YAESU FT 817, 857, 897 AS WELL AS ICOM IC 703, 706 AND 7000
TRANSCEIVERS HAVE BEEN TESTED TO DATE.  THE SOFTWARE IS DESIGNED TO SUPPORT
UP TO 47 DIFFERENT MODELS AND MEETS THE SPECIFICATIONS IN TABLE 1.  TO
PROVIDE A SOFTWARE PACKAGE THAT CAN BE USED BY DEVELOPERS.  MDSR SOFTWARE
RELEASE V2R4 WILL HAVE AN EXTERNAL FREQUENCY COUNTER INPUT FOR RADIOS THAT
DO NOT HAVE A COMPUTER AIDED TRANSCEIVER CAT INTERFACE.  TO UPGRADE AN
OLDER ANALOG RADIO TO SDR CAPABILITY AT LOW COST.  TO USE SOFTWARE FOR THE
DEMODULATION AND MODULATION OF USB, LSB AND CW AM AND FM PLANNED FOR THE
FUTURE WITH A STANDARD SOUNDCARD SERVING AS THE ANALOG TO DIGITAL
CONVERTER.  TO WRITE SOFTWARE THAT RUNS ON WINDOWS BASED PLATFORMS WINDOWS
2000, XP, VISTA AND WINDOWS 7 AND CAN BE QUICKLY INSTALLED AND CONFIGURED
BY ANY AMATEUR.  TO ENSURE THAT THE REQUIRED HARDWARE IS SIMPLE AND EASILY
REPRODUCIBLE, AND TO REQUIRE A MINIMAL AMOUNT OF MEASUREMENT EQUIPMENT THE
MDSR SOFTWARE IS USED AS THE MEASUREMENT TOOL FOR SETUP.  CREATION OF 12
KHZ LOW INTERMEDIATE FREQUENCY LIF RECEIVE SYSTEM HOW TO EXTRACT THE 455
KHZ IF SIGNAL FROM A RADIO SINCE THE EARLY DAYS OF SUPERHETS, 455 KHZ HAS

SDR UPGRADE FOR ANALOG HF RADIOS BRING THE BENEFITS OF DIGITAL PROCESSING
TO YOUR VETERAN HF TRANSCEIVER.  ALEX SCHWARZ, VE7DXW  MOST MODERN
COMMERCIAL HF TRANSCEIVERS USE DIGITAL SIGNAL PROCESSING DSP TO ENHANCE
PERFORMANCE.  DSP, PARTICULARLY IF THE PROCESSING IS AT INTERMEDIATE
FREQUENCIES, OFFERS SUPER SHARP FILTERING AT AS MANY BANDWIDTHS AS DESIRED,
WITHOUT THE NEED FOR ADDITIONAL CRYSTAL FILTERS.  IN ADDITION, DSP CAN
PROVIDE FAR MORE EFFECTIVE NOISE REJECTION THAN OTHER TECHNIQUES AND CAN
PERFORM MANY OF THE MODULATION AND DEMODULATION TASKS PREVIOUSLY PERFORMED
BY ANALOG CIRCUITRY.  THOSE WITH OLDER TRANSCEIVERS STILL HAVE EQUIPMENT
THAT MAY BE MORE THAN ADEQUATE IN TERMS OF RF PROCESSING.  THIS SDR IF AND
AUDIO UPGRADE ALLOWS THE OLDER, BUT EFFECTIVE, RF STAGES OF EARLIER
TRANSCEIVERS TO BE COUPLED TO A DSP BACK END TO PROVIDE AN OPTIMUM MIX OF
TECHNOLOGY, WHILE PRESERVING THE LOOK, FEEL AND INVESTMENT OF EARLIER
RADIOS.  THIS PROJECT WILL RESULT IN AN ADAPTER THAT CAN PLUG INTO A
CRYSTAL FILTER SOCKET, DIGITIZE THE IF SIGNAL AND DEMODULATE IT USING
SOFTWARE AND THEN PLAY THE AUDIO THROUGH THE COMPUTER SPEAKERS OR CONNECTED
HEADPHONES.  PROJECT OBJECTIVES THIS GROUP EFFORT FIRST ESTABLISHED A SET
OF OBJECTIVES FOR THIS PROJECT.  THE OBJECTIVES INCLUDED TO CREATE A
SOFTWARE AND HARDWARE INTERFACE THAT IS USABLE FOR DIFFERENT MODELS OF
‰  END OF 40 WPM TEXT  ‰  QST DE W1AW  ƒ