Newsgroups: rec.radio.amateur.misc Path: elroy.jpl.nasa.gov!decwrl!csus.edu!netcom.com!wa2ise From: wa2ise@netcom.com (Robert Casey) Subject: DR1200 InterMOD reduction mod file Message-ID: Keywords: intermod Organization: NETCOM On-line Communication Services (408 241-9760 guest) Date: Fri, 30 Apr 1993 02:03:57 GMT Lines: 40 copied from packet: Msg# TSF Size Date Time Arrived #Rd Seq # Msg ID Route 612 BF 2607 21-Apr 1643z 24-Apr 0 (002799 - 28806_W0LJF ) [] K0ZL ==> MODS@USBBS "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 ciruit. While the intermod hasn't gone away entirely (I'm not done with it yet!), it has diminished enough to make the rig usable on packet AND voice now. 73 de Bill, K0ZL@W0LJF.#NECO.CO.NOAM =============================================================================== Note: I haven't tried or verified this. proceed at your own risk. WA2ISE