7L5

The Tektronix 7L5 is a low frequency (10 Hz – 5 MHz) spectrum analyzer plug-in for 7000-series scopes. It has built-in digital storage, so it will work fine in non-storage mainframes such as the large-screen 7603. It also features digital scale and marker level/frequency (6 digits) readout, and a "max hold" function.

Manuals – Specifications – Links – Pictures

According to the 070-2184-01 manual, instruments with a serial number below Β070000 are missing the B − (Save A) feature and the corresponding button on the front panel. The military version is called PL-1391/U and is also lacking the B − (Save A) feature.

Key Specifications

Input frequency	10 Hz – 5 MHz
Drift	< 5 Hz/h
Resolution bandwidth	10 Hz – 30 kHz in ×3 / ×10 steps
Sweep rate	10 s/Div to 0.1 ms/Div in 1−2−5 sequence plus Auto
Residual FM	< 40 Hzp-p (< 1 Hz from 50 Hz/Div to 2 kHz/Div)
Outputs	Horizontal, Video, Calibrator
Input impedance	L1 input module: 50 Ω L2 input module: 75 Ω L3 input module: 50 Ω, 600 Ω or 1 MΩ selectable (75 Ω, 600 Ω or 1 MΩ for the L3-1)
Log Sweep Option	250 Hz to 222.25 kHz by digitally combining three decade sweeps (250 Hz—2.25 kHz, 2.25 kHz—22.25 kHz, 22.25 kHz—222.25 kHz), 2.5 s sweep time

Options

No.	Log sweep display	Tracking generator	LED Readout
21	•
25		•
28			•
30	•	•
31	•		•
32		•	•
33	•	•	•

Links

• 7L5 page @ amplifier.cd with internal photos
• 7L5 in operation @ youtube
• L1-GC

====Documents Referencing 7L5====

Document	Class	Title	Authors	Year	Links
Tekscope 1975 V7 N3.pdf	Article	A 5 MHz Digitally-Controlled Spectrum Analyzer		1975	7L5
TekWeek (partial) October 10, 1975.pdf	Article	Spectrum analyzers require high technology	Thor Hallen • Dave Friedley	1975	Spectrum Analyzers • Pentrix • 7L5 • 5L4 • 7L12 • 7L13 • 1401 • 491 • 1405 • 1502 • 1503
AX-3535.pdf	Application Note	Crystal Device Measurements Using the Spectrum Analyzer	Morris Engelson	1977	7L5 • 7L13 • TR502
Tekscope 1977 V9 N3.pdf	Article	Digital Storage for a Microwave Spectrum Analyzer	Dennis Smith • Don Kirkpatrick	1977	7L18 • 7L5 • 155-0157-00 • 155-0158-00
Tekscope 1977 V9 N2.pdf	Article	Measuring Harmonic Distortion with a Spectrum Analyzer	Ken Matheson	1977	FG504 • 7L5 • 5L4N
Tekscope 1978 V10 N3.pdf	Article	Spectrum Analyzer Applications in Baseband Measurements	Morris Engelson	1978	7L5 • L3 • 013-0182-00
AX-3406-1.pdf	Application Note	EMI Applications Using the Spectrum Analyzer	Morris Engelson	1979	7L5 • L1

Prices

Year	1976	1980	1988
Catalog price	$4,500	$7,075	$12,500
In 2023 Dollars	$24,300	$26,400	$32,400

According to an internal memo, in 1979 annual sales were estimated at 454 units.

Pictures

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  7L5 Opt. 33 in 7633 mainframe

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  7L5 Opt. 32

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  7L5 Opt. 25

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  7L5 in 7844

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  7L5 Opt. 25 without B - (Save A)

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  Front Panel of 7L5

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  Back side of 7L5 front panel

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  Complete IF Assembly of 7L5

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  Complete IF Assembly of 7L5

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  RF Module (Vertical Control Board and 1st LO assembly) of 7L5

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  Sweep board of 7L5

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  7L5 A and B oscillator control board front side

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  7L5 A and B oscillator control board back side

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  Front side of Tune Reference A board

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  Back side of Tune Reference A board

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  Front side of Tune Reference B board

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  Back side of Tune Reference B board

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  Front side of A oscillator board

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  Back side of A oscillator board

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  Front side of B oscillator board

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  Back side of B oscillator board

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  Later revision of 7L5 digital storage and average board - front side

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  Later revision of 7L5 digital storage and average board - back side

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  Tektronix 7L5 Transverse Interface Board

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  Tektronix 7L5 Transverse Interface Board

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  Top view of L3 plugin assembly

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  Bottom view of L3 plugin assembly

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  7L5 prepared for servicing the sweep and reference boards

7L5 Opt.25 tracking generator plug-in

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For internal pictures see the repair section.

Components