# Observation of torapezoido wave about AM transmitter

There is a method of observing the torapezoido wave to the method of easily judging the quality of the end steps amplitude modulation circuit like the AM collector modulation circuit (amplitude-modulation circuit). Because torapezoido shape of waves was observed by "Design and production of AM wireless microphone" that can be received on the radio of the medium wave, it explains torapezoido wave.

## Torapezoido wave and the observation method

There is a method of observing the torapezoido wave to the method of easily judging the quality of the end steps amplitude modulation circuit like the AM collector modulation circuit ( the amplitude-modulation circuit). This makes the oscilloscope XY mode, connects X axis with the power supply in the end steps, applies the voltage that changes with the audio signal, and is a measurement of the antenna output voltage in Y axis putting it.

The antenna output voltage corresponding to it can be recorded when the power-supply voltage on the collector side changes hour by hour if it measures it thus, and the shape of waves that lays the trapezoid is observed. It becomes AM modulated waveform that a trapezoid and diagonal part should be straight. Because the trapezoid becomes an isosceles triangle in 100% modulation, it is obvious whether 100% modulation modulates well.

## Observation of torapezoido wave actual

Torapezoido is a meaning of trapezoid. Because the shape of waves where torapezoido wave had just laid the trapezoid had been, it came to be called like this.

### Torapezoido wave that modulates up to about 100%

It is torapezoido wave that adjusts AM wireless microphone by this figure, and modulates up to about 100%.

Because a trapezoid and diagonal part is straight, it is understood that the amplitude modulation with a good linearity hangs.

Even when the overmodulation ,in a word, the modulation of 100% or more is put, it is a circuit of 100% because of the dynamic range of the low frequency amplification circuit that modulates only this side a little.

The oscilloscope used THS710 of Sony Tektronix. The coupling of the signal of the horizontal axis is made DC. (horizontal 1V/Div. vertical 20V/Div. It is over 140Vp-p.)

### Torapezoido wave that modulates about 50%

It is torapezoido wave to which this figure modulates by about 50%. I think that I often use it in the place in which it becomes such a shape of waves usually. It is a very beautiful shape of waves.

As for the speech wave, a usual voice is not a single sine wave, and if the level is constant, becomes such a shape of waves.

### Torapezoido wave when not adjustment of tank circuit

When do the detuning of the tank circuit by torapezoido wave that modulates up to about 100%, it becomes such a shape of waves.

When the adjustment shifts greatly by feeling after time when the tank circuit is not adjusted and the antenna by the hand, it becomes such a shape of waves.

The adjustment of the tank circuit in the end steps including the antenna is very important in the end steps amplitude modulation circuit because the voice is distorted when becoming it like this.

## Linearity of amplitude modulation of transmitter

It is the one that this measured the linearity of the AM modulation. This is thought to be a shape of waves and the same in the upper half of torapezoido waveform that modulates up to about 100%.

I think that I do a so-so characteristic as a collector modulation.

The sound that was not inferior compared with a usual wireless broadcasting was though the modulation was multiplied in the music of the CS digital broadcasting, and it had heard it on the radio of the medium wave.