AMT1.3 EARLIER, I MADE MENTION OF USING THE INTERNAL TONE GENERATOR FOR DISPLAY ALIGNMENT. I CHECKED MY UNIT AND FOUND THAT THE TONE GENERATOR IS VERY ACCURATE. THE TONES WERE WITHIN .15 HERTZ EACH AND WITHIN .1 HERTZ OF BEING 170 HZ APART. THAT IS GOOD ENOUGH TO CALIBRATE MY DISPLAY ANY DAY! WITH ALL OF THE ABOVE MODS INSTALLED, IT IS EASY TO USE THE TONE GENERATOR FOR SUCH CALIBRATION. FIRST USE THE PTT SWITCH TO DISABLE THE PTT. THEN SEND THE AMT-1 AN ESCAPE D COMMAND. THAT WILL PUT IT IN THE ASCII MODE. NOW SHORT THE AUDIO INPUT AND OUTPUT WITH THAT ADDED SWITCH. YOU SHOULD HAVE ONE OR TWO LIGHTS LIT ON THE RIGHT SIDE OF THE AMT-1 FREQUENCY DISPLAY. BY FLIPPING THE TX DATA INVERT SWITCH BACK AND FORTH AND USING THE YELLOW LIGHTS ON THE DISPLAY TO ALIGN IT, YOU CAN ASSURE THAT YOU ARE EXACTLY TRANSCEIVE USING AFSK. NOTES FOR THE HECK OF IT: WITH 13VDC FEEDING THE AMT-1 POWER JACK MY UNIT HAS THE FOLLOWING VOLTAGES AT THE NOTED POINTS: 12V TEST POINT......+12.91V +5V LINE.............+4.75V -V LINE........-7.55V AT C1 YOU MUST USE A WELL FILTERED SUPPLY ON THE AMT. IF THERE IS MUCH RIPPLE ON IT, IT WILL AFFECT THE PROPER OPERATION OF THE DEMODULATOR BUT DOES NOT SEEM TO AFFECT THE TRANSMITTED TONE QUALITY. I KNOW OF ONE UNIT THAT WAS OPERATED WITH ONE VOLT OF RIPPLE ON IT AND YOU COULD NOT TELL IT BY LISTENING TO THE TONES. THEY WERE PERFECT AND OF PROPER FREQUENCY. GOOD LUCK..... DE GARY-AG0N