‰ NOW 40 WPM ‰ TEXT IS FROM DECEMBER 2006 QST PAGES 31, 33 AND 92 ‰ Q MODULATORS AND AUDIO DRIVERS AND PEAK THE RF AMPLIFIER CAPACITOR. THEN SWITCH TO THE OPPOSITE SIDEBAND AND ADJUST THE AMPLITUDE AND PHASE TRIMPOTS FOR ZERO NOISE OUTPUT. ALTERNATE BETWEEN THE TWO TRIMPOTS, AS THESE TWO ADJUSTMENTS BECOME INCREASINGLY CRITICAL ‰ FROM PAGE 92 ‰ 113 2 3 276 ON 4D 415 Wireless Society KQ6AR 621 2 7 2,002 SJV K4YNZ 227 2 ARTICLE. AUDIO SECTION THE TOP HALF OF THE PC BOARD CONTAINS ALL OF THE AUDIO CIRCUITRY. THERE ARE NO PC BOARD TRACES CONNECTING THE TWO HALVES, AND IT IS OKAY TO CUT THE BOARD INTO SEPARATE FUNCTIONAL BLOCKS FOR PACKAGING FLEXIBILITY, OR TO USE THE AUDIO AND RF PORTIONS OF THE CIRCUITRY IN OTHER PROJECTS. SPEECH AMPLIFIER THE SPEECH AMPLIFIER DRIVES A PASSIVE LOW PASS FILTER USING TWO SERIES INDUCTORS AND THREE SHUNT CAPACITORS. THE COMBINATION OF THIS LOW PASS FILTER AND THE MIXER IF PORT FILTERS LIMITS SPEECH FREQUENCIES TO JUST OVER 3 KHZ FOR NATURAL SOUNDING SPEECH AND GOOD SPECTRAL PURITY. THERE IS NO RIPPLE IN THE AUDIO PASSBAND. ANALOG SIGNAL PROCESSOR THE ANALOG SIGNAL PROCESSOR AND BASEBAND AMPLITUDE AND PHASE TRIM CIRCUITRY ARE TAKEN DIRECTLY FROM FIGURES 9R56 AND 9R35 OF EMRFD. THE POSITION OF THE SIDEBAND SELECT SWITCH IN THE SIGNAL PATH ALLOWS SWITCHING WITHOUT READJUSTING THE AMPLITUDE AND PHASE TRIMMERS. FOR MOST APPLICATIONS, ONE SIDEBAND WILL BE USED EXCLUSIVELY, AND THE SIDEBAND ‰ FROM PAGE 92 ‰ Hickory Lake Contest Club K2NNY 737 1 4 1,165 NNY KD8SQ 509 2 2 1,018 OH Findlay RC W8FT 155 2 20 616 OH CT RI Contest Group W1R 239 2 2 562 CT W7JQ ADJUSTING THE GAIN DISTRIBUTION FROM MIC INPUT TO PA OUTPUT FOR MINIMUM DISTORTION WILL BE DISCUSSED IN AN UPCOMING ARTICLE. RF AMPLIFIER THE EXCITERS OUTPUT RF AMPLIFIER USES A COMMON GATE JFET. THIS STAGE PROVIDES A BROADBAND RESISTIVE TERMINATION TO THE MIXER RF PORT IQ SUMMING JUNCTION TO ISOLATE IT FROM VARIATIONS IN IMPEDANCE AT THE EXCITER OUTPUT. THE RF AMPLIFIER HAS RELATIVELY LOW GAIN, GOOD HARMONIC SUPPRESSION AND A VERY CLEAN 0 DBM SSB SIGNAL AT THE OUTPUT. THIS IS AN APPROPRIATE LEVEL TO DRIVE A LINEAR AMPLIFIER, BALANCED MIXER OR TRANSVERTER. IT IS ALSO A LOW ENOUGH LEVEL THAT IT IS EASY TO ADJUST THE EXCITER WITH SIMPLE EQUIPMENT. THE EXCITER OUTPUT SIGNAL MEETS FCC REGULATIONS FOR DIRECT CONNECTION TO AN ANTENNA FOR FLEA POWER EXPERIMENTS. THE TRANSMITTER IN FIGURE 2 ADDS THE SIMPLE TWO TRANSISTOR CIRCUIT IN FIGURE 5, COPIED DIRECTLY FROM FIGURE 2R93 IN EMRFD, FOR 0R5 W PEP OUTPUT. THE SEVENTH ORDER CHEBYCHEV LOW PASS FILTER ON THE OUTPUT IS NON CRITICAL AND ASSURES A CLEAN SIGNAL THAT EASILY MEETS FCC REGULATIONS. SEE THE ACCOMPANYING TEXT IN EMRFD FOR A COMPLETE DESCRIPTION. SEVERAL OPTIONS FOR HIGHER POWER WILL BE EXPLORED IN A FUTURE ‰ FROM PAGE 92 ‰ W2WHP 1320 2 30 4,646 NLI AA2DC 1430 2 2 4,020 NLI AA0BA 952 2 2 3,198 NE N3XLS 865 2 6 3,010 EPA Sullivan County AR Group W1YT 552 2 9 1,760 NH WA4NKL 647 2 3 1,670 GA K9KL 1242 1 2 1,501 WI AB5CY 565 2 3 1,180 AR ‰ END OF 40 WPM TEXT ‰ QST DE W1AW ƒ