3L5

The Tektronix 3L5 is a 50 Hz — 1 MHz spectrum analyzer plug-in for 560-series scopes.

It is very similar to the 1L5 and can be used to measure the spectrum of signals. In conjunction with the 015-0107-00 "Swept Frequency Generator" (tracking generator), the 3L5 can also be used to make scalar frequency response measurements. A video filter switch was added to the later SNs (1971 Catalog). 3L5 is based on the swept-frontend design, where the first local Oscillator is swept for the spectrum scan. It is a full semiconductor design except for the final output amplifier, which uses a 8416 vacuum tube.

75 Ω Version

There is also a 75 Ω version of the 3L5. Its input is on the rear, via a coaxial connector. A lever on the front panel switches between two frequency ranges:

• 10 kHz - 1 MHz
• 18.010 MHz - 19 MHz

Timebase Support

3L5 requires a timebase plug-in in the horizontal compartment to operate. Timebase plug-in units with serial no listed and below require modification 040-0413-00 to provide the sweep signal to the 3L5 (To pin 18 of the plug-in connector).

Time Base	SN#
2B67	15180
3B1	4040
3B3	4270
3B4	740

Key Specifications

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Center Frequency Range	50 Hz to 990 kHz
Dispersion Range	10 Hz to 100 kHz
Input Impedance	≈ 1 MΩ // 30 pF
Input Voltage	Max. 300 V (DC + peak AC)
Vertical Resolution	Video - .1 v/div to 100 v/div, LIN - .001 V to 2V RMS
Internal Cal Signal	5 kHz ±1%
First LO Out	≥1 MHz (Sweep), ≥1 Vp-p into ≥1 kΩ
Recorder Out	5 mV to 15 mV into 600Ω
Weight	≈6 pounds

Pictures

1 MΩ version

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  1 MΩ Version

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  1 MΩ later version with Video Filter Switch

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  LHS

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  RHS

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  Top

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  Bottom

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  Internals - 3MHz Filter, 2nd LO(3.1MHz) and 2nd mixer.

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  Internals - 3MHz Filter, 2nd LO(3.1MHz) and 2nd mixer.

75 Ω version

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  75 Ω version of 3L5, front

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  75 Ω version, front/top

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  75 Ω version, left

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  75 Ω version, top

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  75 Ω version, bottom left

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  75 Ω version

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  75 Ω version

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  75 Ω version, back