7L13

The Tektronix 7L13 is a 1 kHz to 1.8 GHz Spectrum Analyzer plug-in for 7000-series scopes. From 1977 on, a modified version with coverage up to 2.5 GHz was available upon request (no official option listed in the catalog).

Manuals – Specifications – Links – Pictures

It 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.

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

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

• Tektronix 7L13 @ barrytech.com
• Tektronix 7L13 @ radiomuseum.org

Prices

Year	1974	1976	1980
Catalog price	$6,500	$7,500	$10,500
2020 Dollars	$34,100	$34,100	$33,000

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 1^st mixer, with a 1^st LO frequency between 2.095 GHz and 3.895 GHz. At spans of 50 kHz/Div and below, the 1^st LO (a YIG oscillator) is fixed (stabilized by a PLL) and the 2^nd LO is swept.

The 1^st IF filter is 10 MHz wide, centered at 2.095 GHz. With a 2^nd 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 (3^rd LO at 95 MHz).

At the 10 MHz 3^rd 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

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Display examples

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  7L13 displaying a POCSAG FSK signal at 162 MHz (variable persistence storage on a 7623)

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