Tuesday, January 31, 2017

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 :

IC-7300 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 :

Gently bend the legs of capacitor at desired angle, and try if they fit between the soldering points between elements before soldering. 
And this is how it's look after adding the capacitor:


After soldering check the surface against any short circuit around tiny traces. 
Don't forget to clean the surface with amount of IPA alcohol or similar stuff and secure the capacitor to the top of  IC1501 with small piece of double sided adhesive tape, or single drop of nail enamel borrowed from your girlfriend or wife :-)

Final look :

 
Good luck with the mod. Please post the comment below if You'll do the mod with success.
If You feel You can't do the mod yourself, better ask a friend. 
Of course You can send the radio here, I'll do it for You.   

NOTE: 

I AM THE RIGHTS OWNER OF THIS DOCUMENT. 

ANY UNAUTHORIZED COPYING WITHOUT ASKING IS DENIED. 

IF YOU WANT TO PUBLISH THE MOD ON YOUR SITE/BLOG YOU ARE ALLOWED TO DO SO, POINTING THE ORIGINAL SOURCE. 

THANK YOU.  

 

9 comments:

  1. My comment is more of a question. Some Icoms have a serious problem of ALC overshoot where you set the power to a low level to drive an amplifier, say 20w, but when you first key up the radio peaks at over 100w before the ALC engages and brings the power down to 20w. Have you tested your mod to see if it causes an overshoot problem?

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    Replies
    1. No I did not.
      It was not the target of the mod, BUT as far as I know from friends some of them reporting "spikes" in 7300 out of box.
      To be honest, I did not experienced any overshoots in mine - except visual observations (BEFORE I PERFORM THE MOD) - kind of peaks of PO on meter bar.
      On the other hand no any ID drain current peaks/spikes or voltage drop were observed at the same time.
      I am using 2SD2931 SSPA with 7 to 10W drive and 7300 for almost a Year.
      BTW, signing with a ham call is nothing to be ashamed of ;-)
      Good luck 73 !

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  2. Many thanks, great job!!!! It's just that I wanted. It's horrible to have to shout sticked at the mic in order to get only 30w. I'm trying to do the mod, it seems so simple. THANKS AGAIN!!!

    EA3CA

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  3. Hi!

    Just finished solderin my rig, testing here as i write, and itś seems to put the TX power up on SSB. Not so much as a peak power put the average seems ok too with my normal speaking voice and not just whistling.. Making more test and gathering reports tonight. OH3EVM

    ReplyDelete
    Replies
    1. Terve, tnx for info, please don't forget to lower the MIC and PROC values.
      In my cases Mic gain at 25-35% and PROC at 2 max 3 is good enough but of course personal settings matters.
      73!

      Delete
  4. This Type of Mod was also popular with other rigs like the TS-940. The Mod doesn't change the maximum output. It changes the average talk power. (It's called the time constant)Two different things. Many Hams are tinkers.

    ReplyDelete
    Replies
    1. Hi. Of course you're right. And I'll say this is obvious. Modifying radios is not a thing to newbies, so "low SSB power" is kind of mental shortcut. Will add "average" to be more specific.
      73

      Delete
  5. As N2GYN commented, this mod attempts to increase average power, i.e., talk power. This is different than PEP. I strongly encourage the author to be more specific than "low power on SSB." Leaving it vague will cause a flurry of responses explaining that your low power measurement is coming from using a low quality watt meter and that a high quality peak reading meter in needed (in this case it is not a PEP measurement but average power)

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  6. This comment has been removed by the author.

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