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{{Oscilloscope Sidebar | | |||
title=Tektronix 491 | | |||
summary=Spectrum Analyzer 10 MHz to 40 GHz | | |||
image=Tek 491.jpg | | |||
caption=Tektronix 491 | | |||
introduced=1967 | | |||
discontinued=1980 | | |||
manuals= | |||
Need Service Manual | |||
* [[Media:070-0598-01.pdf| Tektronix 491 Instruction Manual {Qservice Scan} (PDF, OCR)]] | |||
* [[Media:050-0692-03.pdf| Tektronix 491 Band C Oscillator Replacement Modification (PDF, OCR)]] | |||
* [[Media:Tek 491 mod wa.pdf|Tektronix 491 Mod WA (PDF, needs OCR)]] | |||
* [[Media:Tek 491 fcp nov 1966.pdf |Tektronix 491 Factory Calibration Procedure, November 1966 (PDF, needs OCR)]] | |||
* [[Media:Tek_491_Catalog_Spec_1967.pdf| Tektronix 491 Introduction Spec (PDF, OCR)]] | |||
* [[Media:Tek_491_Catalog_Spec_1979.pdf| Tektronix 491 Final Spec (PDF, OCR)]] | |||
}} | |||
NOTE: Due to severe performance limitations, it was replaced by the completely redesigned 492 in 1980 | |||
The '''Tektronix 491P''' is a spectrum analyzer with a frequency range of 10 MHz to 40 GHz. The minimum resolution bandwidth is 1 kHz, and provides measurement resolution proportional to the frequency accuracy or span. | |||
Front panel inputs/outputs are: RF INPUT (A) [[BNC connector]] (50Ω, 10 MHz to 275 MHz); RF INPUT (B) [[N connector]] (50Ω, 275 MGHz to 2 GHz); WAVEGUIDE (C) [[N connector]] (50Ω; 12.4 GHz to 40 GHz); and a dual function 1 MHz MARKERS OUT [[BNC connector]] (With the INT REF FREQ in the ON position a 1 MHz marker outputs to this connector. With the INT REF FREQ in the OFF position EXT REF FREQ IN “same” [[BNC connector]] accepts an external signal between 1 MHz and 5 MHz (1 to 5 V peak to peak) applied to the connector becomes the reference frequency for the phase lock operation). | |||
* | Rear panel inputs/outputs are: TRIG IN [[BNC connector]] (20 Hz to 100 kHz, ≥0.2V); SAW OUT [[BNC connector]] (75mV/div); and RECORDER [[BNC connector]] (≥4 mV/div of displayed signal in LIN mode, DC-coupled, into 600Ω load impedance). | ||
{{BeginSpecs}} | |||
{{Spec | Frequency Range | | |||
* Coaxial Input Bands 10 MHz to 12.4 GHz (Band A-1: 10 MHz to 275 MHz; Bands B-2 & 3: 275 MHz to 2 GHz; and Bands C-4, 5, & 6: 1.5 GHz to 12.4 GHz) | |||
* External Waveguide mixers: 12.4 MHz to 40 GHz (Band 7: (Ku) 12.4 GHz to 18 GHz; and Bands 8: (K) 18 GHz to 26.5 GHz, and (Ka) 18 GHz to 40 GHz) | |||
CAUTION: Signals stronger than +15 dBm applied to the input or mixer will damage or burn out the mixer diodes }} | |||
{{Spec | Dispersion Range (plus 0 Hz) | 200 kHz/div to 10 MHz/div in 1-2-5 sequence }} | |||
{{Spec | Resolution Bandwidth Range | 6 dB bandwidths from 1 kHz to 100 kHz }} | |||
{{Spec | RF Input impedance | 50 Ω }} | |||
{{Spec | Maximum Safe Input Power | -30 dBm for linear operation and +15 dBm (25 mW) diode mixer power limit }} | |||
{{Spec | IF Attenuator Range | 0 dB to 51 dB, in combinations of 1, 2, 4, 8, 16, and 20 dB }} | |||
{{Spec | Sweep Speed Range | 0.5 s/div to 10 µs/div in 1, 2, 5 sequence; Uncalibrated to approx 1.25 s/div }} | |||
{{Spec | Triggering Modes | Internals, External, and Line. 100 V maximum input (DC + peak AC) }} | |||
{{Spec | Display Dynamic Range | ≥40 dB | |||
{{Spec | Dynamic Range | 80 dB (Max sensitivity of -110 dBm minus Max input power of -30 dBm) }} | |||
{{Spec | Calibrator Frequency | 200 MHz }} | |||
{{Spec | Included Accessories |Two Instruction Manuals; 6-ft, 50Ω coaxial cable, BNC-BNC; 6-ft, 50Ω coaxial cable, N-N; 2-ft, 50Ω coaxial cable, TNC-TNC; 12.4 GHz to 18 GHz waveguide mixer; 18 GHz to 26.5 GHz waveguide mixer; 26.5 to 40 GHz waveguide mixer; 10 dB attenuator N type fittings; 20 db attenuator N type fittings; two BNC male to N female adapters; two BNC female to N male adapters; Waveguide mixer adapter; power cord; dust and rain cover; 3 to 2 wire adapter; blue light filter; amber light filter; clear CRT protector plate; ornamental ring; mesh filter (installed); two one-ampere fuses; and 1/2 –ampere fuse }} | |||
{{Spec | Weight | Portable: 13.6 kg (30 lbs) ; Rackmount: 18 kg (40 lbs) }} | |||
{{Spec | Power | 90 − 136 V<sub>AC</sub> in three ranges, 48 to 440 Hz; 180 – 272 V<sub>AC</sub> in three ranges, 48 to 440 Hz. At 115 V<sub>AC</sub>, 60 Hz, 55 W }} | |||
{{Spec | Operating Atmospherics | Temperatures: -15 °C to +55 °C; Humidity: Five cycles (120 hours) of MIL-STD-202C Method 106B; Altitude: Up to 4.6 km (15,000 ft) }} | |||
{{EndSpecs}} | |||
== | ==Options== | ||
* | * Opt. 01: Limit Frequency Range to 10 MHz to 2 GHz | ||
* Opt. 02: Limit Frequency Range to 1.5 GHz to 40 GHz | |||
==Pictures== | ==Pictures== | ||
<gallery> | <gallery> | ||
Tek 491 front trace.jpg | Tek 491 front trace.jpg | ||
Line 42: | Line 76: | ||
</gallery> | </gallery> | ||
[[Category:Spectrum Analyzers | [[Category: Spectrum Analyzers]] | ||
Revision as of 22:22, 5 July 2019
NOTE: Due to severe performance limitations, it was replaced by the completely redesigned 492 in 1980
The Tektronix 491P is a spectrum analyzer with a frequency range of 10 MHz to 40 GHz. The minimum resolution bandwidth is 1 kHz, and provides measurement resolution proportional to the frequency accuracy or span.
Front panel inputs/outputs are: RF INPUT (A) BNC connector (50Ω, 10 MHz to 275 MHz); RF INPUT (B) N connector (50Ω, 275 MGHz to 2 GHz); WAVEGUIDE (C) N connector (50Ω; 12.4 GHz to 40 GHz); and a dual function 1 MHz MARKERS OUT BNC connector (With the INT REF FREQ in the ON position a 1 MHz marker outputs to this connector. With the INT REF FREQ in the OFF position EXT REF FREQ IN “same” BNC connector accepts an external signal between 1 MHz and 5 MHz (1 to 5 V peak to peak) applied to the connector becomes the reference frequency for the phase lock operation).
Rear panel inputs/outputs are: TRIG IN BNC connector (20 Hz to 100 kHz, ≥0.2V); SAW OUT BNC connector (75mV/div); and RECORDER BNC connector (≥4 mV/div of displayed signal in LIN mode, DC-coupled, into 600Ω load impedance).
Key Specifications
{{Spec | Display Dynamic Range | ≥40 dBFrequency Range |
CAUTION: Signals stronger than +15 dBm applied to the input or mixer will damage or burn out the mixer diodes |
---|---|
Dispersion Range (plus 0 Hz) | 200 kHz/div to 10 MHz/div in 1-2-5 sequence |
Resolution Bandwidth Range | 6 dB bandwidths from 1 kHz to 100 kHz |
RF Input impedance | 50 Ω |
Maximum Safe Input Power | -30 dBm for linear operation and +15 dBm (25 mW) diode mixer power limit |
IF Attenuator Range | 0 dB to 51 dB, in combinations of 1, 2, 4, 8, 16, and 20 dB |
Sweep Speed Range | 0.5 s/div to 10 µs/div in 1, 2, 5 sequence; Uncalibrated to approx 1.25 s/div |
Triggering Modes | Internals, External, and Line. 100 V maximum input (DC + peak AC) |
Dynamic Range | 80 dB (Max sensitivity of -110 dBm minus Max input power of -30 dBm) |
Calibrator Frequency | 200 MHz |
Included Accessories | Two Instruction Manuals; 6-ft, 50Ω coaxial cable, BNC-BNC; 6-ft, 50Ω coaxial cable, N-N; 2-ft, 50Ω coaxial cable, TNC-TNC; 12.4 GHz to 18 GHz waveguide mixer; 18 GHz to 26.5 GHz waveguide mixer; 26.5 to 40 GHz waveguide mixer; 10 dB attenuator N type fittings; 20 db attenuator N type fittings; two BNC male to N female adapters; two BNC female to N male adapters; Waveguide mixer adapter; power cord; dust and rain cover; 3 to 2 wire adapter; blue light filter; amber light filter; clear CRT protector plate; ornamental ring; mesh filter (installed); two one-ampere fuses; and 1/2 –ampere fuse |
Weight | Portable: 13.6 kg (30 lbs) ; Rackmount: 18 kg (40 lbs) |
Power | 90 − 136 VAC in three ranges, 48 to 440 Hz; 180 – 272 VAC in three ranges, 48 to 440 Hz. At 115 VAC, 60 Hz, 55 W |
Operating Atmospherics | Temperatures: -15 °C to +55 °C; Humidity: Five cycles (120 hours) of MIL-STD-202C Method 106B; Altitude: Up to 4.6 km (15,000 ft) |
Options
- Opt. 01: Limit Frequency Range to 10 MHz to 2 GHz
- Opt. 02: Limit Frequency Range to 1.5 GHz to 40 GHz