The AM Forum

Here is a neat tool to use with your scope.

http://preciserf.com/shop/station-monitor-trapezoid-qrp/

Chuck

Not to come off as being critical but I don't see how using the trapezoid pattern test with this device would provide any true benefit unless audio is directly sampled from the audio stages as in monitoring a plate modulated rig. And using it in linear fashion it is more puzzling.  To me this works similarly to a Heath station monitor. An SB610 is less expensive.

It is for use with a linear amplifier to determine if the amplifier is linear or not. That's where its value lies. It lets linear amplifier users see typical user problems like clipping or the results of incorrect bias. It does not evaluate the modulating device or the device driving the linear amplifier.

It does a similar thing as when a vector scope is connected to the input and output of an audio amplifier and a diagonal trace is plotted revealing any nonlinearities and phase shifts.

Instead of plotting a diagonal line like the vector scope used for audio tests, it makes a trapezoid familiar to most ham users by detecting the audio envelope of the input-side signal and applying that to one channel of the scope.

This helps the measurement to be accurate because it eliminates issues present when using two RF sources as X and Y inputs to a scope.

"It is designed for transceiver output levels of up to 100 Watts driving linear RF amplifiers." - so, it gives a visual indication in a familiar format for the benefit of those who do not have a high level modulated RF amplifier such as in a plate modulated transmitter, but instead who have a small-size low level modulated transceiver that they use with a linear amplifier for AM. There are many hams that do that for their AM.

The SB-610, and multiphase MM-2, when used in this fashion, do the same thing.