The TS570 and 480 sound very good on AM, especially if something other than 
the stock microphone is used.

I use a Shure 444 with my 570, and set the transmit audio equalization of 
Menu #14 to the HB setting.

The stock microphone for the 570 sounds okay on sideband, but has a pretty 
restricted audio range that becomes quite obvious on AM or FM.

Both the 570 and 480 have a separate power setting for AM that will not go 
above 25 watts of carrier output. The radio remembers where you have the AM 
power set, so you don't have to adjust it every time.

Steve, try turning the AM power on your 480 down to 5 watts, or no more than 
10, and driving your 811H with that power on AM.

You can operate the 811H at about 100 watts output on AM without melting 
anything.

To do that, first tune the amplifier to full output with full drive from the 
480 as though you were about to use it on sideband. Then, switch the rig to 
AM, and adjust the power to 5 or 10 watts, whichever gives you the 100 watt 
reading from the amplifier.

Do not retune the amplifier at the lower drive level.

It should then sound amazingly good, and most people won't be able to tell 
it from plate modulated AM.

Some guys down here push the 811H to 150 watts out on AM, but for my money, 
that's running the tubes, and the amplifier's power supply a bit too hard.



Mike Duke, K5XU
American Council of Blind Radio Amateurs