Modifications for the ICOM - RogerK

21-10-1999(AT-500) ICOM AT-500 Tuner HintAuthor: Dave Parlier - dcparlier.nj@worldnet.att.net.MODIFICATION.NET10/12/99The IC AT-500 Auto Tuner has four (4) antenna coax plugs on the rear for various bands.You can solder all band wires needed to a single terminal lug and use only one (1) coax connector, if desired (per ICOM usermanual). If you prefer not to "go inside" , then two short coax pieces fed into a "T" coax connector will feed two separatefrequency ranges (e.g. 80m & 40M) into a single connection point.Dave Parlier W2CGGChatham, NJThis modification is read 822 times.top of page19-07-1998(I290) Icom I290 scan modificationThe objective of the modification is to implement a delay before scanning restarts when, in SCAN-STOP mode on BUSYfrequency, the received signal disappears.The modification will then allow a frequency to be free for a while before scanning resumes.With this modification, it will be given a chance to a signal to come back within a few seconds before the scanning restarts.Now multiple QSOs or poor signals won't be truncated any more because of a too much impatient scanning !WHAT TO DO:Very simple. On the SENSOR UNIT, just solder a jumper between:●●the unused contact of switch S3 (the one corresponding to the TIMER OFF position of the circuit commanding the SEL pin ofIC1)and the EMPTY signal of connector J3 (this is the extreme pin nearest S2 on the SENSOR unit)ATTENTION, there are some errors on the electrical scheme that I possess reference A-0488 :●●The S3 switch is represented in position TIMER OFF and not ON as written. You have to reverse labels OFF and ON.The signals BUSY and EMPTY on connected are reversed. EMPTY (SQ1) is on the extreme left pin of S3 and BUSY is on 2ndpin of this connector S3. In fact, the switch S2 is drawn in the BUSY position and not EMPTY.HOW IT WORKS :The TIMER starts when pin SEL of IC1 goes to 0V. When the TIMER is running, the scanning is halted.The scanning also stops when the BUSY signal is low level (0V) on pin SQL of IC1.Let us suppose that a signal is received. Then BUSY goes to 0V and scanning halts. At the same time the EMPTY signal , which isthe inverse of BUSY, goes to 5V and the TIMER remains off.If the received signal disappears BUSY goes high and EMPTY low, then the TIMER is enabled and starts running. It also maintainsthe scanning in halt mode.If, at the end of the TIMER delay, no signal has come back then the scanning restarts.If a signal comes back before the end of the TIMER delay then the BUSY signal returns to 0V and maintains the scanning in haltmode. In the meantime the TIMER will run until the end of its delay without any action on the process.The TIMER delay is chosen with the R32 potentiometer on the SENSOR UNIT. The minimum value is about 4 to 5 seconds whichis perfect for this working mode.Small modification .... great effect !Gabriel F6DQM @ FF6PTT.FRPA.FRA.EUThis modification is read 407 times.top of page