Modifica riduzione intermodulazione per ALINCO DR-1200

[RADIOMOD]

                         DR-1200 INTERMOD REDUCED

                                 ALINCO DR-1200


INTERMOD REDUCTION CAUTION: THE FOLLOWING PROCEDURE INVOLVES DESOLDERING SMD (SURFACE MOUNT DEVICES). IF YOU ARE NOT QUALIFIED TO WORK ON SMD DEVICES OR DO NOT HAVE THE PROPER EQUIPMENT, DO NOT ATTEMPT THIS MOD! SEEK PROFESSIONAL TECHNICAL ASSISTANCE. THE ORIGINATOR OF THIS MODIFICATION IS NOT RESPONSIBLE FOR ANY LOSS INVOLVING THE PERFORMANCE OF THIS MODIFICATION. CAUTION: THIS RADIO EMPLOYS STATIC SENSITIVE DEVICES. SUITABLE MEANS SHOULD BE EMPLOYED TO ASSURE A STATIC-FREE ENVIRONMENT PRIOR TO BEGINNING WORK ON THIS RADIO.

1. REMOVE POWER AND ANTENNA FROM RIG
2. REMOVE BOTTOM COVER
3. LOCATE C-19, LEFT SIDE FRONT OF BOARD (CLEARLY LABELED, NEAR Q3).
4. REMOVE C-19: SUCK UP THE SOLDER AND CAREFULLY PRY AWAY FROM BOARD WHILE STILL WARM.
5. SAVE THE CAPACITOR IN CASE YOU GOT THE WRONG PART!
6. REASSEMBLE THE RADIO, NO RETUNING NECESSARY. This capacitor connects D1 (back to back diodes) to the first IF line. D1 is supposed to be a "limiter". Unknown why Alinco chose to put in such a limiter, as the integrated IF chip IC-1, an MC3357, has a built- in limiter. Also, the Kenwood TM-231 which uses nearly the same layout and circuit, doesn't have such a circuit. While the intermod hasn't gone away entirely , it has diminished enough to make the rig usable on packet AND voice now.