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2000GTL Low AM peaks-SSB OK

S

Seven01

Member
Jan 7, 2011
6
0
11
Louisville KY
Greetings all...
This 2000GTL has 20w peaks on SSB and only 7-8w peaks on AM, even after a power jump, which should make the AM swing up to 20w or so.
Since it has full power output on SSB I would not think there are any issues with the tuning caps after the final...
Modulator/driver/final changed too.
What am I missing here..? TNX for the help!
 

Check the setting of the Automatic Modulation Control (AMC) as this is one circuit that limits the peak AM power independently of the SSB output that is controlled by the ALC.
 
AMC is opened up...
A power jump puts full voltage to the final when in AM mode, allowing the usual 10-12w peaks on AM to go up to about 20w peaks, even with the AM carrier set to 1w...
 
My cobra 2000gtl will only key up 4 watts and swing to about 6 watts....what did you do to yours to get it to put out that much ?
 
Seven01 said:
AMC is opened up...
A power jump puts full voltage to the final when in AM mode, allowing the usual 10-12w peaks on AM to go up to about 20w peaks, even with the AM carrier set to 1w...
Click to expand...

wouldnt that mess it up for using with a low drive amp?
 
Seven01 said:
AMC is opened up...
A power jump puts full voltage to the final when in AM mode, allowing the usual 10-12w peaks on AM to go up to about 20w peaks, even with the AM carrier set to 1w...
Click to expand...

What's the point? You get half a S point....
 
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That power jump sounds like trouble to me , I guess we can leave that to someone more qualified an that's certainly not myself . But as the old saying goes 10 lbs of s*%t in a 5 lb bag . JMO

Sent from my NB09 using Tapatalk
 
OK fellerz...your getting off topic here...

This 2000gtl has been put back into completely stock situation and still the low AM output peaks, with full 20w SSB peaks.
If there were any disc caps 'after' the final that were out of sorts, then the SSB output would be affected also.

Now to address the other stuff...
A typical stock GTL (with AMC intact) will do 4-5w AM carrier with maybe 8-10w voicepeaks.
Turning the AM AMC open will produce a peak of maybe 12-14w voicepeaks AM.
With ALC open you will see 15-20w voicepeaks SSB.
In order to make the final do the same output in AM as it does SSB, you have to do a 'power jump' as some call it. In SSB mode, full voltage of about 13v is applied to the final. To make the final do the same output in AM as it does in SSB, you need to make that higher voltage go to that final. The usual method is to take the Final Bias setting jumper (one goes to the driver, the other to the final) off the test pins and solder the wire to the center pin (collector) of the modulator transistor. This will push the final as hard in AM as it does in SSB.
This will make the AM carrier jump way up, so you will need to lower the AM carrier output, via several methods I ain't gonna get into right here.

(I should have just said this radio is stock...and could have avoided all this other stuff..LOL)
 
When you pull that carrier back down, you pull the peak with it unless you do some sort of swing mod. But running the final that hard in AM is most assuredly going to end in destruction.
 
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The 2K will NOT swing hard at all on Am as it is... id just leave it alone and/or sell it and get an export if you want that swing...
 
Seven01 said:
AMC is opened up...
A power jump puts full voltage to the final when in AM mode, allowing the usual 10-12w peaks on AM to go up to about 20w peaks, even with the AM carrier set to 1w...
Click to expand...
4 watts X's 4 = 16 watts or 100% modulation. Keep that amc in line unless you have external processing. 1 watt swinging 20 = super trucker audio.
 
Sounds like just plain old volting the final. Those old 1969's are fairly rugged but may not last as long as you'd like leaving it volted. Plus, on the receiving end no one is probably going to notice much of a difference. Just my 2 cents and no offense intended..... 73's.
 
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