1L5
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.
