HP 22A, 83620A, 24A manual Amplitude Modulation

Amplitude Modulation

Amplitude modulation can be accepted from an external source at the AM connector or can be internally generated by synthesizers with Option 002. The damage level of the AM input is f15 V DC. The input impedance of the AM connector is 500. A jumper on the A10 ALC board allows you to change the input impedance to 2 kR (See “Adjustments” in the Service Guide.) The AM can be scaled either linearly at 100% per volt or exponentially at 10 dB per volt.

When internal AM is chosen (Option 002), the rate and depth are set by softkeys in the AM menu. The waveform menu provides a choice of sine, square, triangle, ramp, or noise waveforms. The monitor menu lets you output the internally generated modulation waveforms to the rear panel AM/FM OUTPUT connector. The AM output is scaled the same as it is generated, either 100%/V or 10 dB/V. This connector can drive 5OQ or greater. The monitor menu also lets you display the value of the AM depth.

UNLVLED Message

The maximum leveled output is limited by the synthesizer’s maximum leveled output power specification. (Individual synthesizers may be capable of greater leveled output power; the unleveled message indicates the actual limit.) Amplitude modulation adds to and subtracts from the reference RF power level. If an IJNLVLED message appears on the display, you may be trying to modulate beyond the synthesizer’s maximum output power capability.

OVRMOD Message

The maximum AM depth is limited to approximately 90% by the detector’s ability to sense low power levels. If you try to amplitude modulate too deep without using deep AM mode (explained later), you will see an l&??t$:~D message displayed on the message line. Also, if you modulate below -20 dBm ALC level without using deep AM mode or below -50 dBm with deep AM or search ALC mode, you will see an OVRt4OD message.

Dynamic Range

The ALC and attenuator combination (when an optional attenuator is present) are automatically set by the synthesizer to keep the ALC in its most accurate range (0 to -10 dBm). This is called the coupled attenzlator operating mode.

For applications where modulating across an attenuation switch point is undesirable, you can uncouple the attenuator and manually set the power level of the ALC and the attenuator.

For example, setting the power level to 0 dBm in coupled mode will give an ALC level of 0 dBm and 0 dB of attenuation. In uncoupled mode, the attenuator can be set to 10 dB and the ALC to +lO dBm, giving 0 dBm output power and greater AM depth potential. The ALC can now be varied over its entire range and the attenuator remains at a fixed level.

M-14 Operating and Programming Reference	HP 8360
User’s	Handbook