How to Setup a Modern Day
Transceiver for AM

by Steve Ickes, WB3HUZ

 If you are like many people, you found AM after you've been in the hobby a while and have purchased one of the newer all-mode transceivers. Although these radios most often find use on SSB, most can work and sound very respectable in the AM mode - IF SETUP PROPERLY. If you follow the steps below, you should be able to adjust your rig for good sound on AM.

1. Determine the maximum PEP capability of your rig. You can do this by referring to the manual or setting the thing up for max output on SSB and observing a PEP wattmeter. If you don't have a PEP wattmeter, tune up the rig in the CW mode for the maximum carrier output. If your rig has tubes in the final, you'll need to do this anyway.
2. Reduce the power output to one-quarter (0.25) the power found in Step 1. Do this by adjusting the carrier level or power output control.
3. Start with the microphone gain set at minimum. Increase the gain while talking into the mic in a normal tone of voice and observing the ALC meter reading, till you see the meter just barely deflect. Reduce the mic gain slightly from this setting.

  That's it, you're ready to get on the air on AM. However, the setting may not be exactly right but this three step process should get you close. Once you get on the air, ask for an audio report to determine if you need to do any tweaking. If you have an oscilloscope, by all means, use it to adjust your mic gain. Using a scope, you can determine your percentage of modulation and if you are flat-topping.

  If you want to run your transceiver into your linear, follow the same steps (although you shouldn't have to do Step 3 over again) with the linear in line. One important thing to remember is that your linear will be running at about 20 -25% efficiency. So, you may want to get your calculator out and determine how many watts you can run without exceeding the plate dissipation rating of your linear. Crapped out tubes in your linear is a real bummer. Also remember that AM is a 100% duty cycle mode, as opposed to 30-50% for SSB. So the tubes and the power supply in your linear will be working much harder. You may not want try to squeeze every last watt out of your rig. Err in the side of safety.

  The AM mode can be a lot of fun. Although it is most often associated with older, tube type gear, modern day transceivers can produce some very good sounding AM when properly adjusted. Come on and join the fun.

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21 June 1997