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Icom 718- ALC modification for AM possible?

H

High Miler

Active Member
May 30, 2005
298
5
26
Pennsylvania
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...
 

High Miler said:
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...
Click to expand...
The 718 ain't no CB!! Just what were you thinking of "clipping/removing"??? Don't forget to add a power mic and echo. If you hang the 718 from a celing fan at home or if mobile from the roof with 18" bungee cords and shake the steering wheel back and forth you can get lots of SWIIIIING :LOL:
 
You might try simply reducing the power (does the 718 allow that?) and setting the mike gain to a level that allows the carrier to audio ratio to = around 70-80 %. If you are looking for an Amateur radio to "swing", you're not going to get it. In truth, an AM carrier will NOT have a huge amount of that over-rated and much-vaunted "SWANG" so coveted in the CB world.
I run AM with my 706's and, set up properly, they do pretty well as rice boxes go. :)

73

CWM
 
High Miler,
Very simply, you can't do much to 'improve' AM modulation with any of the later ham radios. They were never designed for AM, and at best you will only have 'low level' AM available. Other than the novelty of it, I honestly don't know why anyone would want to use AM anyway. But that's personal preference...
- 'Doc
 
Hook948 said:
High Miler said:
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...
Click to expand...
The 718 ain't no CB!! Just what were you thinking of "clipping/removing"??? Don't forget to add a power mic and echo. If you hang the 718 from a celing fan at home or if mobile from the roof with 18" bungee cords and shake the steering wheel back and forth you can get lots of SWIIIIING :LOL:
Click to expand...


My my my... It don't have to be no CB there Mr. Clever, Havn't you heard AM on the ham bands before??? Guess if you run them there 'cb's you wouldn't know that now would you?? I've heard some heavily modified solid-state rigs that sound good, One of them being a modified Kenwood radio as your pic so looks...

So come on guys give me a break, there's am'ers on 160,75, and 40 all the time, and their not all Plate modulators either... I wasn't lookin' for no top gun modulated swing-thing or any of that crap, just a simple question to see if it was possible...

Thanks for the answers from you guys that weren't so darn critical, as for the rest of you, man your in the wrong hobby if you can't offer a little piece of info without comming off like a block head.... That's not what the hobby is about...

As for the radio, it is set-up with a 25 watt dead-key going into a al1200 ... Mic gain kept low enough to keep from comming against the alc to hard, and has a very nice AM sound, very natural... I was trying to get away from the back kick every so often when I hit certain words right...

Other than that my Kenwood TS870 stays on the al1200, along with rack gear for hi-fi ssb work on 75/40 meters...

I picked up the little 718 for peanuts and it had a nice sound on am, I thought with a bit of improvement it would be nice to play with...

Sorry that some of ya woke up on the wrong side of the bed this morning... You all have a good day.
 
High Miler,
After your explaining a little more about what you're doing, I think the advice to lower your carrier power might be a good one. Not being all that familiar with the '718 or the '870, but from experience with other radios of the same 'vintage', the 25 watts of carrier is sort of 'pushing' things. Especially into an AL-1200 (or any of the other amplifiers around). Not that you're nearing the limits of the '1200, but because it will ceretainly magnify any distortion presented to it (and it is getting close to that limit, believe it or not).
The last transmitter I used that did well with AM was a 'Ranger II'. Not that I was supposed to be using AM, because of the license, but just had to try it once, you know?
- 'Doc

[Same call, sort of, but had a 'K' on the end of it and an 'N' in the front part. Lord, that dates me! ;)]
 
I just ran with the clipping and swing things you posted. :roll: Now that you have explained what you are really looking for, you've already got good advice from the other guys. I still say if it's SWING you want then the bungee cord trick will give you probably more than you were looking for.:LOL: Yes my TS-850 sounds "OK" on AM when the rig and the mic EQ are adjusted correctly but it's NOT what I would call a AM rig. If you are looking for a cheap rig that has a nice TX audio to play on AM with, My vote is for one of the Yaesu FT-101's ;)
 
Yes sir your right about the 'ole 101's,when done up right they work well...

I have a DX60 heavily modified and works very well on AM... I guess I wanted something new to dig my fingers into...

Have a good week... Guess the Icom is what it is, still a nice little radio for what I paid for it.. We'll find use for it somewhere...

'73s....
 
I have a Heath DX-60B for AM use also. Nice older rig.Mine is not modified except to double the value of the series capacitors in the audio chain and I installed an outboard PTT circuit that also handles antenna changeover.The rig will pass just about anything through the modulator so the best thing one can do for the DX-60 is use a good microphone. I use a Sennheiser MD-421professional broadcast microphone.It's kind of like a $100 saddle on a $10 horse but it sounds like $1,000,000 on the air.My next 80m AM project is an RCA BTA-1S which is a 1Kw watt AM broadcast transmitter that is sitting in my basement.It runs a pair of 4-400's in the final plate modulated by another pair of 4-400's.Now if I could only find the time to convert it. :?
 
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W5LZ said:
Not being all that familiar with the '718 or the '870, but from experience with other radios of the same 'vintage', the 25 watts of carrier is sort of 'pushing' things.
Click to expand...

LZ is dead on.

Most rice boxes are only rated for 100 watts PEP. General rule of thumb is 100% modulation on AM yields a PEP that is 4 times the carrier power. 4 x 25 = 100.

Factor in that AM is 100% duty cycle...I'd probably feel comfortable running the radio at about 15 watts carrier, and following that up with a amp to push up to about 200 carrier.

Then sit back and warm the aether!!
 
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