• You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
  • Click here to find out how to win free radios from Retevis!

Icom 718- ALC modification for AM possible?


A 9v battery hooked up as a Negative Voltage into the ALC port on the back of the radio, through a potentiometer.
 
  • Like
Reactions: TetroideTom
One simple trick that works on many HF rigs, is injecting line level audio into the radios carrier or drive control circuit. If these are potentiometers, it's easy to inject through a coupling cap to block DC. If the audio lacks high frequency response, look for high value bypassing caps, shunting the audio to ground, and reduce their value so they are only effective at RF. ALC will still require adjustment to unlock this potential.
 
I was wondering if anyone could tell me of a ALC modification for allowing the Icom 718 to swing forward with modulation rather than the ALC circuit clipping the power before decent modulation is achieved?

I have pulled out the service manual but before clipping/removing any part I thought I would check and see if anyone knows for sure how to defeat the ALC to a certain extent to allow forward modulation..

Thanks much in advance...
I have my 718 set to where power on H its carrier is 25 & when I speak it goes to 100-120 depending where I am. Before on a rms meter it modulated backwards but after adjusting the ALC along with the AM power it works nice. I’m told it sounds smooth & it’s about 95% modulation. I have to put my mic setting on #4 to keep it sounding nice anymore it’s muffled sounding. I had Matt @Icom service put in a new vfo & 2 diodes because the receive was low. Radio was gifted to me because of those 2 issues & $220 did it all. Radio was clean if it hadn’t been I’d bought a different one. Now it is lined up everything’s fixed but I wanted AM to work nice now it does. Hope you get yours right. There’s azz wipes that say shit because they can’t turn a screw.
 

dxChat
Help Users
  • No one is chatting at the moment.
  • @ David K. Aldridge:
    Hi. I acquired a Galaxy Saturn Turbo that goes into xmit mode, xmit LED lights, but no output at all in any mode when monitoring on a radio right next to it. Nothing. It receives fine. Also, in the amp module on back, there are MRF454's in there. Those weren't factory, were they? Any clues? Thanks.