The Tektronix 7L13 is a 1 kHz to 1.8 GHz Spectrum Analyzer plug-in for 7000-series scopes, designed by Fred Telewski who also led the TR502 development.

Tektronix 7L13
1.8/2.5 GHz Spectrum Analyzer
Tektronix 7L13

Compatible with 7000-series scopes

Produced from 1974 to 1981

Manuals

From 1977 on, a modified version with coverage up to 2.5 GHz was available upon request (no official option listed in the catalog).

The 7L13 is similar to the 7L12 but occupies three module bays, adds a marker function, offers resolution bandwidth down to 30 Hz, and improves sensitivity by 10 dB. It also displays the center frequency in the CRT readout as well as on a LED display.

When used in a four-compartment 7000 series mainframe, it must occupy the two vertical slots and the left horizontal slot.

The TR502 tracking generator is designed to work with the 7L13 up to 1.8 GHz.

After 1982, the 7L13 was superseded by the similar 7L14 which added digital storage.

Key Specifications

Input frequency 100 kHz – 1.8 GHz (modified version up to 2.5 GHz)
Span 200 Hz/Div – 100 MHz/Div
Sweep 1 μs/Div to 10 s/Div (1−2−5), manual, external
Resolution bandwidth 30 Hz – 3 MHz in decade steps
Sensitivity −128 dBm at 300 Hz to −80 dBm at 3 MHz
Vertical scale 10 dB/Div, 2 dB/Div or linear
Reference level −110 dBm – +30 dBm in 10 dB steps
Video filters 30 kHz, 300 Hz or 10 Hz
Features
  • Automatic phase lock
  • CRT readout of center frequency
  • UNCAL indicator
  • built-in calibrator 50 MHz, −30 dBm
  • Base line clipper

Links

Documents Referencing 7L13

Document Class Title Authors Year Links
Tekscope 1974 V6 N1.pdf Article 30 Hz resolution at gigahertz frequencies - a new direction in spectrum analysis Fred Telewski 1974
Tekscope 1975 V7 N5.pdf Article A High-stability 100 KHz to 1.8 GHz Tracking Generator Fred Telewski 1975
TekWeek (partial) October 10, 1975.pdf Article Spectrum analyzers require high technology Thor Hallen Dave Friedley 1975

Prices

Year 1974 1976 1980
Catalog price $6,500 $7,500 $10,500
In 2023 Dollars $40,100 $40,100 $38,800

In TekWeek 10 Oct 1975, Thor Hallen says

The 7L13 is a 3-wide plug-in and is the most expensive plug-in we make. The price is $7,500.

According to an internal memo, in 1979 annual sales were estimated at 537 units.

Internals

The input signal passes a 0 to 60 dB step attenuator, a 1.8 GHz low-pass filter, and a 3 dB isolation pad before the 1st mixer, with a 1st LO frequency between 2.095 GHz and 3.895 GHz. At spans of 50 kHz/Div and below, the 1st LO (a YIG oscillator) is fixed (stabilized by a PLL) and the 2nd LO is swept.

The 1st IF filter is 10 MHz wide, centered at 2.095 GHz. With a 2nd LO at 2.2 GHz, the signal is mixed to a 105 MHz IF, amplified, filtered again (105±1.5 MHz) and mixed down to 10 MHz (3rd LO at 95 MHz).

At the 10 MHz 3rd IF, resolution filters (300 kHz L/C, 30 kHz, 3 kHz or 300 Hz crystal filters) can be selected. The detector (discrete log amplifier) and video filters follow.

The digital frequency readout is a DVM (Fairchild 3814) working off the the YIG oscillator control voltage, not a frequency counter, which is why it needs to be calibrated before use.

Custom integrated circuits used: 155-0035-00 quad opamp, 155-0042-02 Miller integrator, 155-0056-00 sweep control, 155-0088-00 legend generator.

Pictures

Display examples

Components

Some Parts Used in the 7L13

Part Part Number(s) Class Description Used in
155-0028-00 155-0028-00 155-0028-01 155-0042-00 155-0042-01 155-0042-02 155-0042-03 Monolithic integrated circuit Miller integrator and delay pickoff 5030 R5030 5031 R5031 1401 1401A 1480 1481 1482 1485 26G1 26G2 26G3 314 335 432 434 4701 5B10N 5B12N 5B31 5B40 5B42 5S14N 7B52 7B53A 7B53N 7L12 7L13 7L14 7L18 7S14 AN/USM-281C RG501 Telequipment D63 Telequipment DM63
155-0035-00 155-0035-00 155-0116-00 Monolithic integrated circuit quad op-amp 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
155-0056-00 155-0056-00 155-0056-01 Monolithic integrated circuit sweep control 26G1 26G2 26G3 314 4701 5B10N 5B12N 5S14N 7L5 7L12 7L13 7L14 7L18 7S14 RG501 Telequipment D63 Telequipment DM63
155-0088-00 155-0088-00 Monolithic integrated circuit custom legend generator 7D15 7L13 7L14
Fairchild 3814 156-0306-00 Monolithic integrated circuit 4½ digit dual-slope DVM controller 7A13 7L13 7L18 DM501