Help with AM operation

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  • Updated 2 months ago
I tried running in AM mode recently and a friend recorded my transmission, it was horrible, all distorted and just sounded like total crap, and verified by a few others. I don't think this is rocket science but I could use some advise. I tried the AM carrier slide at 100 down to 30 with no noticeable improvement. I'm sure there's something stupid I'm missing. I'm using a 1kw amp and have the carrier level set for just under 200 watts. 
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bjn644 .

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Posted 2 months ago

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bahillen

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Did you turn off the amp and run flex barefoot?
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Ken - NM9P, Elmer

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1) The "Carrier Level" is not the same as the carrier level setting in other rigs.  It adjusts the percentage of carrier to modulating sidebands which allows "full AM" at 100  or you can back it down to increase the ratio of carrier to audio,  giving more effective modulation up to a point.  But if you turn it back too far, you will have operators with standard envelope detectors complain of distorted audio because there is not enough carrier to decode it (not a problem with SAM detectors or SSB detectors).  

In order to keep the carrier drive to your amplifier in check, use the RF Power control.  That will preserve your carrier to audio ratio.

2) If you use PROC in DX or DX+ mode on AM you WILL get distortion unless you turn your mic gain back more than needed for a standard SSB signal to stay "out of the red."  In fact, I never use DX or DX+ on AM and often don't even use NORM.  I typically only let it peak about 65-80% up to the "Red" when on AM.  (Actually, I listen to my own signal via the Full Duplex method and turn it down until the distortion goes away.)

3) If you have too much BASS either in TX EQ or the TX Filter Low Cut, you can also get distortion unless you cut your mic gain back a little.  

4) You can use the Full Duplex audio monitoring technique and listen to your own signal on a second slice while transmitting to the XVTR port.  It will give you a pretty good indication of what your AM Signal sounds like as you adjust mic gain, TX filters, TX EQ, PROC, DEXP, etc. 

When you are finished testing, then return to normal operation and carefully adjust your drive to your amp with the RF Power Out control in order to stay within your amplifier drive limits.

Hope this helps. 

Ken - NM9P
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bjn644 .

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Thanks Ken. I didn't get a chance to try anything last night, but I did notice that by default the bias and +20db boost was enabled in the setup menu. I'm thinking that that might be causing the distortion.
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W3FJJ

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I run my 6300 , always with RF power level all the way up, then adjust carrier control to set how much carrier
Power I want to run, either barefoot or into amplifier. Then I adjust my audio level, for 100-120 percent modulation. I use a monitor scope, but if you don't have one , use watt meter, on flex, your audio peaks should read about
4 times your carrier power (unmodulated power) . I also use the processor, but in normal mode.
Been getting great audio reports this way for years. Great sounding AM rig..