1L5

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The Tektronix 1L5 is a low-frequency spectrum analyzer for 500-series scopes. It is very similar to the 3L5.

Its center frequency is set on a trio of rotary switches and can range from 50 Hz to 990 kHz. Minimum resolution bandwidth is 10 Hz. It has a 1 MΩ input resistance.

Type 1L5 was sold from 1967 until the end of the classic plug-in scope line. Not particularly accurate in either frequency, bandwidth, or amplitude, it was no match for HP's 141T/8556A/8552B combination in performance, but it was a small fraction of the price.

Although Type 1L5 can operate in any 500-series scope*, it is most useful by far in the Type 549 storage mainframe which allows slow sweeps needed to match the narrower resolution bandwidths.

In conjunction with the 015-0107-00 "Swept Frequency Generator" (tracking generator), the 1L5 can also measure frequency response.

* 531/535/541/545 need a wiring mod to alleviate vertical amp instability.

Pictures

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  549 works fine with 1L5

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  top

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  right

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  rear

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  left

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  front

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  bottom

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  1L5

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  Block Diagram

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  Attenuators and Input

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  Center Frequency Switching

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  Swept Frequency Generator

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  Variable Resolution Amplifier

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  Dispersion Warning Light

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  Output Amplifier

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  Calibrator

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  Interconnecting Plug and Power Distribution

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  Preproduction 1L5 (serial A01)

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  Preproduction 1L5 (serial A01)

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  Preproduction 1L5 (serial A01)

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  Measured frequency response of 3 MHz filter from P90 to P280 with Q290 removed to disable 3.1 MHz oscillator, but powered up. 10 dB/div.

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  Measured frequency response of 3 MHz filter. 1 dB/div.