When using an amplifier for an AM signal, we have always been taught that the amplifier needs to be linear, and if it is not, that distortion products will run up and down the band causing interference to adjacent stations, or even causing out of band emissions. Some might remember the CB linears where most have a mode switch. The labeling on the mode switch is usually AM or SSB. With SSB, they bias up the transistors to have increased idle current. With AM, there is no bias at all...this is real close to class C since we are biased at cutoff. I have converted a number of these CB amplifiers to 10m operation over the last 25 years. They all need an attenuator and / or some RF feedback to reduce the gain such that a 3 watt carrier makes about 20 watts RF. Switching the mode switch to SSB is necessary for that mode, but with AM, all it seems to do is increase the gain a bit. Running AM linear at the edge between class B and class C works, does not splatter, and it increases the efficiency of AM linear operation somewhat. So today I wanted to put this to the test using my Gonset GSB-201 amplifier. This amplifier runs a quad of 572B tubes at ~ 1500V plate. I recently changed the "too-small" filament chokes for a single bifiliar wound choke. This got rid of the high input SWR problem on 80M, similar to the issue on the Heath SB-200. I also use a small MFJ tuner on the input as this keeps the SWR on the exciter at 1:1 on all bands. This amplifier can do 140 watts AM with headroom for 130% positive peaks. That comes out to around 725 watts PEP. The following test was done on 20M and a RF output of 100 watts. What makes this easier to do is the "Kill A Watt" that I have. I plug the Gonset into it, and it can read volts, amps, KVA, and watts. Watts are volts X amps X the cosine of the angle between V&A. If the angle is zero degrees, Cosine of 0 is 1, and therefore VA = W. So with the "Kill A Watt", I read 242 watts just to turn on the filaments, and the high voltage. Figure half the total is filament power, and the other half is HV power. This Gonset uses a full wave bridge rectifier with a negative lead choke, and a big bleeder resistor. The exciter was a Flex 3000, and was modulated at about 85% in all cases. One consequence of running the "linear" at almost zero idle current is the modulation percentage at the output is greater then at the input. In this case the output seems close to 95% downward modulation when the input was close to 85%. This is a form of distortion, sure...but consider what you gain if the exciter can be backed off to peaking 90% instead of 100%. In a plate modulated exciter, going to 100% with the occasional peak "white-lining" the scope display indeed does cause splatter. Backing off the driver audio, and still getting 100% modulation after the "linear" is a good thing. Jim Wd5JKO Note: I was using two scopes with slightly different sweep rates. In all cases the unmodulated carrier was 4 cm in height.