494

Manuals – Specifications – Links – Pictures

The Tektronix 494 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. The P suffix designation indicates GPIB Programmability.

In 1988, the 494A /494AP successor model was introduced.

Key Specifications

Frequency Range	10 kHz to 1.8 GHz 1.7 GHz to 5.5 GHz 3 GHz to 7.1 GHz 5.4 GHz to 18 GHz 15 GHz to 21 GHz External Waveguide mixers: 18 GHz to 325 GHz
Frequency Span	50 Hz/Div to 500 MHz/Div in 1–2–5 sequence, plus 0 Hz and MAX
Resolution Bandwidth	30 Hz, then 100 Hz to 1 MHz in decade steps (-6 dB)
RF Input	50 Ω, max. +30 dBm (1 W) CW or 75 W peak pulse (1 µs, 0.1% duty factor)
RF Attenuator	0 dB to 60 dB, 10 dB steps
Reference Level	–117 dBm to +40 dBm
Sweep Speed	10 sec/div to 20 µs/div in 1, 2, 5 sequence
Video Bandwidth Filter	Normal, Wide: 1/30, or Narrow: 1/300 of resolution bandwidth
Triggering Modes	Free Run, Line, Video, Single, External
Display Dynamic Range	80 dB
Calibrator (Cal out)	50 Ω, –20 dBm ±0.3 dB at 100 MHz
Weight	24 kg (52 lbs) with standard accessories
Power	90 − 132 VAC, 48 to 440 Hz; 180 – 250 VAC, 48 to 440 Hz, 210 W max
Operating Environment	–15 °C to +55 °C, Humidity: Five cycles (120 hours) MIL-STD-810; Altitude: Up to 4.6 km (15,000 ft)

Options

• Opt. 08: Delete external Mixer capability
• Opt. 12: Help mode text in English + German
• Opt. 13: Help mode text in English + French
• Opt. 14: Help mode text in English + Spanish
• Opt. 20: General Purpose 12.4-40 GHz Waveguide Mixer Set
• Opt. 21: High performance 18 to 40 GHz WM490 Series Waveguide Mixer Set
• Opt. 22: Same as Opt. 21 plus WM490U (40-60 GHz) Waveguide Mixer
• Opt. 30: Rackmount with front panel I/O
• Opt. 31: Rackmount with rear panel I/O
• Opt. 32: Benchmount
• Opt. 41: Digital Microwave Radio Measurement Enhancement package: Provides wider bandwidth preselector, 30Hz video filter with 100 kHz resolution bandwidth and a 5 MHz/Div span.
• Opt. 42: Replaces MARKER/VIDEO input port on the rear panel with a 110 MHz IF output port that provides a 6 dB signal bandwidth ≥ 5 MHz
• Opt. 45: MATE/CIIL language interface

Links

• Comparison of 494 with 492 and 7L18
• 49x Service notes @ John Miles KE5FX

Connections

Front panel inputs/outputs are: RF INPUT 50Ω (N connector), CAL OUT (BNC connector), LO OUTPUTS (SMA connectors), EXTERNAL MIXER RF INPUT (TNC connector), and Camera Power. The LO outputs can be used to connect an external waveguide mixer like the WM490 series, or to connect a TR503 tracking generator.

Rear panel inputs/outputs are: PROBE POWER (Provides operating voltages (+5V, -15 V, +15 V; 100 mA max each) for active probes); HORIZ|TRIG (EXT IN) BNC connector (A dual function connector: When in External Triggering mode the connector is an AC coupled input for trigger signals. When the TIME/DIV selection is EXT the connector is a DC coupled input for horizontal sweep voltages); MARKER/VIDEO (EXT IN) BNC connector (Available on instruments without Opt. 42 only. See 110 MHz IF for Opt. 42 instruments. This connector interfaces the spectrum analyzers with a Tektronix 1405 TV Adapter to display an externally-generated marker) 110 MHz IF (OUTPUT) BNC connector (Available on Opt. 42 utilizing the HORIZ (OUTPUT) connector. This connector provides 110 MHz IF output with a bandwidth greater than 5 MHz. Input external video signals into the PEN LIFT connector); HORIZ (OUTPUT) BNC connector (Supplies a 0.5 V/div horizontal signal); VERT (OUTPUT) BNC connector (Provides access to the video signal with 0.5 V for each division of displayed video above or below the center line.)

NOTE: Both HORIZ and VERT output signals are driven from digital storage if it is on. Both signals are driven from the analyzer sweep and video amplifier stage if digital storage is off;

PEN LIFT (OUTPUT) BNC connector (Provides access to a TTL compatible signal to lift the pen of a chart recorder during sweep retrace. This signal is always derived from the spectrum analyzer sweep. In Opt. 42 instruments, use this connector to input external video signals if pin 1 of the ACCESSORIES connector is grounded; 10 MHz IF (OUTPUT) BNC connector (Provides access to the output of the 10 MHz IF); EXT REF IN BNC connector (A 50Ω input for a 1, 2, 5, or 10 MHz external reference signals, within -15 dBm to +15 dBm level. Input signals must be a sinewave with a duty cycle symmetry of 40% to 60%, or ECL or TTL); J104 ACCESSORY female DB25 connector (Provides external video input selector on Pin 1 and external preselector out on Pins 2 and 3, Pin 5 is ground.); IEEE STD 488 PORT GPIB interface (Added to all "P" suffixed instruments)

Accessories originally included

Operator’s Manual; Programmer Manual; 6-ft 50Ω coaxial cable N-N; 18-inch 50Ω coaxial cable BNC-BNC; N male to BNC female adapter; Diplexer Assembly; Power Cord; spare fuses; CRT filter set consisting of amber and gray light filters plus mesh filter

Pictures

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  Internal top view

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  Internal bottom view

Custom ICs used in the 494

Page	Model	Part nos	Description	Designers	Used in
155-0035-00	M053B	155-0035-00 • 155-0116-00	quad op-amp	Mike Metcalf	3110 • 3S7 • 3T7 • 492 • 492A • 492AP • 492P • 494 • 494P • 496 • 496P • 4010 • 4011 • 4012 • 4013 • 7L5 • 7L12 • 7L13 • 7L14 • 7L18 • 7S11 • 7T11 • 7S12 • S-6 • 1461 • 4602 • P7001 • 613 • 653
155-0106-00	M101	155-0106-00	normalizer	Walt Ainsworth	J20 • 492 • 492A • 492AP • 492P • 494 • 494P
155-0157-00	M180	155-0157-00	digital storage vertical control	Don Kirkpatrick	7L5 • 7L14 • 7L18 • 491 • 492 • 492A • 492BP • 492PGM • 494 • 494A • 495 • 496 • 497P
155-0158-00	M181	155-0158-00	digital storage horizontal control	Don Kirkpatrick	7L5 • 7L14 • 7L18 • 491 • 492 • 492A • 492BP • 492PGM • 494 • 494A • 495 • 496 • 497P
155-0285-00	155-0285-00	155-0285-00	leveling circuit		494
155-0286-00	155-0286-00	155-0286-00	distribution amplifier		494
155-0287-00	155-0287-00	155-0287-00	mixer		494

Custom ICs used in the 494P