Date: Sat, 24 Mar 90 15:00:22 EST From: mgb@tecnet1.jcte.jcs.mil Subject: IC-2SAT TX/RX mod I read a posting a few weeks ago where a gentleman was interested in any mods for the IC-2SAT that extended transmit or receive frequency range. I didn't pay much attention to it then, but when the XYL got one for me as a birthday present... that attitude changed markedly! :-) Well, I gathered up all I could find on the issue and broke out the soldering iron and took apart the radio that was less that one day old. (OH NO Mr. Bill!!!!) Here's the straight scoop and I HAVE tried this but you still proceed at your own risk (in case you were so foolish as to not know that :-) Take the battery cover off the bottom and remove the two screws. Remove two screws directly behind PTT button. Remove one screw where handy-carry strap goes. Gently pull on the front half of the radio and the radio will split apart but don't pull TOO far because the front half of the radio is still attached to the back half with that flexible plastic film wiring stuff. Fold front half to the right and lay it down. WARNING: The battery//cover release button can now pop out and a little itsy-bitsy tiny spring can take off for parts unknown. (Ask me how I know this... I spent 2 HOURS looking for that little sucker!) Pull the button out of the case NOW and watch out for that blasted little spring! All work is done on the circuit board inside the FRONT half of the radio (the part that you just pulled off). EXTENDED RECEIVE: Look along the RIGHT side of the circuit board and about halfway down the right side you will see a tiny circuit board that is mounted VERTICALLY on it, aligned from top to bottom. Look at the TOP of this little tiny board and you will see a normal diode (D-9) that is vertically mounted on the vertical board. Sounds confusing, but you can't miss it, it's right on the top end of the board. Cut this diode. Don't try to unsolder it... CUT IT. Take my word on it. WARNING: Don't pull the diode away from the board and leave it hanging. When you put the radio back together it is a very close fit and if you short the diode, the radio won't work. The PLL stays unlocked but no damage will occur. (yeah, I did that too :-) If you stop right here and reassemble the radio, you will now have extended RECEIVE capability after you reset the radio according to the instructions in the manual on the first page. And it REALLY is extended. My PLL was still locked up down around 88 Mhz and actually received FM broadcast stations although it obviously sounded BAD! :-) The radio freq. read-out now will go all the way up past 1 GHz, but that's just the dial read-out, check the Channel Indicator and when it goes to a "U" for "Unlocked" you can keep an eye on PLL performance, however I was amazed at where the PLL was locking up and the fact that it was actually receiving (albeit poorly) across a very very wide range. Yes, of course the sensitivity is way down the further you wander from the 144-148 design frequency range but it still is pretty impressive, and the new freqs. can be stored in memory and scanned. EXTENDED TRANSMIT: Look for the big IC directly in the middle of the main board on the front cover (IC-1 40608). Go to the bottom right corner of it. Move your eyes slightly to the right and you will see three chip resisters in a row. Just to the right of THOSE you will see three silk screened dots that are bracketed by a rectangle of white ink lines where a factory diode package would have gone. The "dots" form a triangle with one at the top and two at the bottom. Install a diode (1N914 or equivalent) with the cathode on the TOP dot and the anode on the bottom left dot. This will give you extended transmit from about 138-163 or so. But if you believe that trying to get a diode in there (without shorting out a lot of stuff) is impossible, (and you are very close to being correct) then FORGET this approach. Instead get Icom's diode DA (# 1750000160) and install IT in the same place. I tried using the 1N914, and it was a TOUGH job. It worked but looked horrible and was in imminent danger of falling off. I tried it out, verified that it worked... and pulled it right out. I have the diode DA pack on order now and will do it right when it gets here. I would politely suggest that you forget trying to use the 1N914 unless you have a micro-miniature repair facility at hand. (I did and still didn't like it). To avoid hate mail .... I have to remind you that it is illegal to transmit on the air with this radio out of the Amateur Bands unless a legitimate emergency exists. (Type acceptance and all that.) However if you (like me) plan on using it for a quick and dirty sig-gen into a dummy load, then it is the cat's meow! Mark Bitterlich WA3JPY mgb@tecnet1.jcte.jcs.mil ------------------------------ Copied from the QRZ! Windows Ham Radio CDROM