HP / Agilent 8904A
Multifunction Synthesizer, Refurbished

• Sinewaves dc to 600 kHz
• Square, ramp, triangle dc to 50 kHz
• Direct digital synthesis
• Tone, DTMF, digital sequence modes
• One or two outputs
• One to four internal channels
• AM, FM, Ø, DSBSC and pulse modulation
• External timing control for fast hop
• Available Options, Below

Hewlett Packard 8904A Shown

Product Information
Datasheet	805 KB
Ordering Info
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The HP 8904A Multifunction Synthesizer uses the latest VSLIC technology to create complex signals from six fundamental waveforms.  The standard HP 8904A digitally synthesizes precise sine, square, triangle, ramp, white noise, and dc waveforms and routes these signals to a signal output.  Option 001 adds three more identical internal synthesizers (channels) which either can modulate the first synthesizer or be summed to the output.  Frequency, amplitude, waveform, phase, and destination can be set independently for each synthesizer.  Available modulation types for channel A include AM, FM, ØM, DSBSC, and pulse modulation.  Option 002 adds a second output, providing a second, separate signal for two-channel applications.  Option 003 adds fast hop and digital modulation capability to the HP 8904A.  All this unique capability makes the HP 8904A a powerful new tool for demanding applications like VOR, ILS, FM Stereo, and communications signaling.

Function Synthesizer

The HP 8904A Multifunction Synthesizer delivers synthesizer accuracy, along with six waveforms in a compact, economical package.  Broad sinewave frequency coverage from 0 Hz to 600 kHz with 0.1 Hz resolution make the HP 8904A ideal for a number of low-frequency applications.  In addition to sinewave generation, the HP 8904A has five other standard functions: square, triangle, ramp, dc, and Gaussian white noise.  Of these five, square, ramp, and triangle functions are available from 0 Hz to 50 kHz.  All waveform values in the HP 8904A are DIGITALLY calculated in real time by Hewlett Packard's Digital Waveform Synthesis IC.  The use of this chip results in signals with very well-defined accuracy and exact repeatability.

Option 002 adds a second, identical synthesizer and floating output section to make the HP 8904A TWO synthesizers in one half-rack width measurement.  Frequency, amplitude, waveform, and phase can be independently set for each of the two synthesizers.

Although both synthesizers are independent, the relative phase between the two outputs can be controlled precisely.  Either synthesizer can be varied in phase from 0 degrees to 359.9 degrees with a resolution of 0.1 degree.  Testing phase detectors, servo systems, shaft encoders, sonar, and other phase sensitive two-port devices is easy and accurate with the HP 8904A Option 002.

By adding three more (total of four) internal synthesizers which can modulate or be summed with synthesizer A (channel A), Option 001 is the key to complex signal generation for the HP 8904A Multifunction Synthesizer.  All four internal synthesizers can be set to generate different waveforms, frequencies, amplitudes, and phase offsets at the same time.  These signals then can be DIGITALLY summed before routing to the output.  In addition to summing, Option 001 allows channels B, C, and D to be used as modulation sources for channel A.  The allowable modulation types for channel A are: AM, FM, ØM, DSBSC (Double Sideband Suppressed Carrier) and pulse modulation.  Using summation and modulation, the HP 8904A Option 001 can generate precise VOR composite, ILS composite, and FM Stereo Multiplex composite signals. Only your imagination limits the possibilities for signal generating with the HP 8904A Multifunction Synthesizer.

In addition to the extra channels, Option 001 also adds three sequence modes to the HP 8904A: tone sequence mode, DTMF sequence mode, and digital sequence mode.  These modes make the HP 8904A a powerful tool for generating sequences used in communications signaling.  Tone sequence mode allows entry of sixteen unique sine wave tones, each with an "on-time" and "off-time".  From these sixteen tones, sequences can be built up to a length of 250 tones.  The minimum on and off time duration is 800 µs with 10 µs resolution while the maximum value is 655.35 ms.  Digital sequence mode can generate digital bit streams up to 1000 bits in length.  Minimum period in the digital mode is 100 µs with 10 µs resolution.  On and off "levels" in the digital mode can be set to any value for simulating conventions.  For ease of entry, data may be entered in binary, octal, editing features and three control modes: single sequence, continuously repeat sequence, and manual step-through the sequence.

Option 003 adds the ability to hop the HP 8904A in frequency, phase, and/or amplitude.  Up to 16 frequency/phase/amplitude states can be entered into the "HOP RAM" memory.  To hop, an external device must address the four-bit TTL-level address bus provided on the digital port connector on the rear panel.  As the address supplied to the bus is varied, the HP 8904A will hop to the frequency/phase/amplitude state that corresponds to that address of the HOP RAM memory.  Fast hop can be performed only on channel A.  Phase continuous frequency switching can be done in as little as 8 µs.