492

Manuals – Specifications – Links – Pictures

The Tektronix 492 is a spectrum analyzer with a frequency range of 10 kHz to 21 GHz in coax, and up to 325 GHz with external waveguide mixers (492PGM N/A). The P suffix designation indicates GPIB Programmability.

During the lifespan of the instrument, the specifications and included options were altered several times. A major upgrade was the introduction of the 492A in 1987 which added marker functionality and resolution bandwidths and the 492BP in 1989 which added a counter and increased the displayed dynamic range. The 492PGM is a cost reduced version introduced in 1990. Also see 49X Series Comparison.

Key Specifications

Frequency	Coaxial Input Bands: 10 kHz to 21 GHz External Waveguide mixers: 10 kHz to 325 GHz (applies to 492BP not 492PGM)
Frequency Span (plus 0 Hz and MAX)	492BP: 100 Hz/div to 10 GHz/div; 492PGM: 200 MHz to 1 GHz; both in 1, 2, 5 sequence
Resolution Bandwidth (-6 dB bandwidth)	492BP: 100 Hz to 3 MHz; 492PGM: 1 kHz to 3 MHz; both in decade steps
RF Input impedance	50 Ω
Maximum Safe Input Power	CW: +30 dBm (1 W); Pulse: 75 W Pk (1 µS pulse, 0.1% duty factor)
RF Attenuator	0 dB to 60 dB, 10 dB steps
Reference Level	-117 dBm to +30 dBm
Sweep Speed	10 sec/div to 20 µs/div, 1−2−5
Video Bandwidth	492BP: 0.3 Hz to 30 kHz; 492PGM: 3 Hz to 30 kHz
Memory	NVRAM for up to 9 waveform displays, up to 10 front panel setups, plus 8 K for programming macros
Triggering Modes	Free Run, Line, Video, Single, External
Displayed Average Noise	−30 dBm to −131 dBm
Display Dynamic Range	492BP: 90 dB; 492PGM: 80 dB
Calibrator (Cal out)	50 Ω, -20 dBm ±0.3 dB at 100 MHz
Weight	492BP: 21.8 kg (47 lbs) 492PGM: 21.3 kg (46 lbs)
Power	90 − 132 VAC, 48 to 440 Hz; 180 – 250 VAC, 48 to 440 Hz. At 115 VAC, 60 Hz, 210 W max

Options

• Opt. 01: Internal Preselection. (Limits the first band to 1.8 GHz instead 4.2 GHz). Later became standard
• Opt. 02: Digital Storage. Later became standard
• Opt. 03: Frequency Stabilization & 100 Hz Resolution. Later became standard
• Opt. 07: 75Ω dBmV input and calibration in addition to the normal 50Ω dBm input and calibration. (Not combinable with Opt. 21 and 22; no external mixer capability). Include 42-inch 75Ω BNC-BNC coax cable and BNC male to “F” female adapter.
• Opt. 21: (492BP) High performance 18 to 40 GHz WM490 Series Waveguide Mixer Set
• Opt. 22: (492BP) Same as Opt. 21 plus WM490U (40-60 GHz) Waveguide Mixer
• Opt. 23: GRASP software, PC2A interface, and GPIB cable
• Opt. 27: Epson LT-386SX, GRASP software, PC2A interface, and GPIB cable
• Opt. 28: Compaq Deskpro 386S, Model 40, GRASP software, PC2A interface, and GPIB cable
• Opt. 39: Non-lithium (Silver) batteries for battery-backed memory
• Opt. 41: Digital Microwave Radio Measurement Enhancement package
• Opt. 42: Replaces MARKER/VIDEO input port on the rear panel with a 110 MHz IF output port that provides a 3 dB signal bandwidth ≥ 4.5 MHz
• Opt. 45: (all except 492PGM) MATE/CIIL language interface

Links

• Comparison of 492 with 494 and 7L18
• 49x Service notes @ John Miles KE5FX
• KE5FX GPIB toolkit
• ROM replacement
• Tek 492 DIY USB interface project
• Waveguide Mixers for 492 and 7L18
• YouTube: Tektronix 492 and 496 Portable Spectrum Analyzers
• 067-1137-99 GPIB to accessory controller

Connections

Front panel inputs/outputs are:

• RF INPUT (50 Ω N connector) – Input for RF signals to 21 GHz. If input signal has a DC component, use a blocking capacitor
• CAL OUT (BNC connector) – Provides 100 MHz, –20 dBm signal and a comb of frequency markers 100 MHz apart
• 1ST LO OUTPUT (SMA connector) – Output of the 1st local oscillator, must be terminated into 50 Ω when not connected.
• 2ND LO OUTPUT (SMA connector) – Output of the 2nd local oscillator, must be terminated into 50 Ω when not connected.
• EXTERNAL MIXER RF INPUT (TNC connector, 50 Ω)
• Camera Power

Rear panel inputs/outputs are:

• PROBE POWER – Provides operating voltages (+5 V, -15 V, +15 V; 100 mA max each) for active probes
• HORIZ/TRIG (input, BNC) – In External Triggering mode, AC coupled input for trigger signals; when TIME/DIV selection is EXT, DC coupled input for horizontal sweep voltages
• MARKER/VIDEO (B053575+, output, BNC) – interfaces the 492/492P with a TV Sideband Adapter, such as the Tek 1405, so a marker from the adapter is displayed on the internal video. External video applied to this connector will also be displayed if pin 1 of the ACCESSORIES connector is grounded.
  • Opt. 42 replaces MARKER/VIDEO with 110 MHz IF (output, BNC) – 3 dB signal bandwidth ≥ 4.5 MHz
• EXT PRESELECTOR (B053574 and below) (output, BNC) – variable voltage (approx -0.2 V to +10 V) proportional to center frequency, for preselector bands of Opt. 01 instruments, to drive an external preselector
• HORIZ (output, BNC) – 0.5 V/div horizontal signal
• VERT (output, BNC) – Video signal with 0.5 V/Div
• PEN LIFT (output, BNC) – TTL compatible signal to lift the pen of a chart recorder during sweep retrace. In Opt. 42 instruments this port may also be used for inputting external video if pin 1 of the ACCESSORY connector is grounded.
• 10 MHz IF (output, BNC) – Output of the 10 MHz IF
• J104 ACCESSORY (B053575+ only), female DB25 connector – Provides bidirectional access to the instrument bus.
• IEEE STD 488 PORT GPIB interface – Added to all "P" suffixed instruments

Pictures

492

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  Internal top view

492A

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492BP

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492PGM

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