Modifikation ICOM IC-7300, erhöhung der mittleren Leistung bei SSB von SP3RNZ
Ebenso wie beim IC-7100 ist es auch beim IC-7300 das Problem der zu scharfen ALC-Begrenzung, dass die ALC-Schleife zu schnell arbeitet, um die Signalhüllkurve ausreichend ansteigen zu lassen. Und es geht nicht um die Einstellung der MIC-Verstärkung oder des PROC-Wertes. Im Anhang noch zwei Videos zur Modifikation
ICOM IC-7300 SSB average power MOD
If You are owner of 7300 this MOD should make You more happy looking on your small Icom 7300,
not to mention about saving your throat screaming loud to get more than 30W on SSB.
Quite dissapointing serious factory fooling their users saying that screwed ALC unit is made to comply with the high standards of spectrum purity and A class signal.
So what about their other radios, i.e 746, 756 or any PRO series? Are they piece of *&**(^&^ and should not be used? Kind of bullshit IMO.
At this point I need to pass my sincere KUDOS to Marios SV0CL for his priceless hints, discussion and help.
Here’s a solution – SSB average power (or „talk average power“ ) increase MOD, born after hours spent on examining schematic diagrams, comparing circuit details and ham radio cooperation.
Likewise as in IC-7100 low average SSB power ( but not only SSB – i.e FSK441 and JT6M ) it’s the problem of too sharp ALC limiting making the ALC loop acting too fast to let the signal envelope to rise enough. And it’s not the matter of MIC gain setting nor PROC value. As You probably seen on the video posted in December HERE difference in average SSB power is HUGE at first sight.
Take note that MIC gain and PROC settings remains LOW comparing to this what we can find on various websites concerning low power on SSB, and we are still within 75% of ALC scale!
WARNING : Any mistake can cause serious damage to your radio. So if You are not experienced in SMD soldering or using soldering iron at very FRAGILE enviroment – do not try to perform the operation! I will be not responsible for any damage You can make doing the MOD.
We need to prepare tantallum capacitor, magnifying glasses, and a value of 2,2-4,7uF /16V will do the job for us. The bigger capacitance, the slower ALC rise time. Test proved that 3,3uF works well and could be optimal solution, but 4,7uF will be good as well.
This time we need to add the ALC slowdown capacitor here :
Although 7300 unit is almost the same as 7100, we can see few small changes, mainly in component values.
Apart of on MOSFET transistor added ( changed vs 7100) there’s no difference.
IC-7100 ALC :
Open your 7300 removing both covers, and face the radio left side to You. Having speaker on the right hand, on the left You will see RF UNIT. This is the place we will work.
Take very good magnifying glasses, we will solder our capacitor between VERY small SMD elements.
Look at the MAIN unit and locate region marked RED:
Closer look at PCB :