Icom 718- ALC modification for AM possible?

[Shadetree Mechanic]

The 718 is an excellent AM rig after a few adjustments. Get inside and turn the modulation up and the carrier down. Run the audio into the accessory port in the back.

 

[Shadetree Mechanic]

Icom IC-718 Service Manual

I came across the service manual for the 718, thought I would share. https://www.manualslib.com/manual/792930/Icom-Ic-718.html?page=19#manual

www.worldwidedx.com

 

[NZ8N]

Icoms on AM, external ALC mod

A site dedicated for the AM Radio Amateur and vintage radio. Home of the AM Press/Exchange, The AM Forum (the largest BBS of it's kind),and The AM Classifieds, Photos, Audio, and technical information. Audio and Video chat rooms.

amfone.net

A 9v battery hooked up as a Negative Voltage into the ALC port on the back of the radio, through a potentiometer.

 

[Shockwave]

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.

 

[Mikey1966]

FM is 100% duty cycle, but AM isn't.

I think you’re ass backwards.

 

[Mikey1966]

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.