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.
In conjunction with the 015-0107-00 Swept Frequency Converter (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). The 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
The 3L5 requires a timebase plug-in in the horizontal compartment to operate.
Timebase plug-in units with serial numbers listed 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
| Center Frequency | 50 Hz to 990 kHz |
|---|---|
| Dispersion | 10 Hz to 100 kHz |
| Input Impedance | 1 MΩ // 30 pF |
| Input Voltage | Max. 300 V (DC + peak AC) |
| Vertical Resolution | Video: 100 mV/div to 100 V/div, LIN: 1 mV to 2 VRMS |
| 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 600 Ω |
| Weight | 2.7 kg / 6 lbs |
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 - 3 MHz Filter, 2nd LO (3.1 MHz) and 2nd mixer.
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Internals - 3 MHzFilter, 2nd LO (3.1 MHz) and 2nd mixer.
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Internals - 100 kHz crystal from variable res amp 158-0022-00
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Internals - 100 kHz crystal from variable res amp 158-0022-00
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
Components
Some Parts Used in the 3L5
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 1N3182 | 152-0269-00 | Discrete component | varactor diode | 3L5 • 1L5 • 3T7 • 492 • 465M • 7844 • 2465 |
| 8416 | 154-0413-00 • 157-0116-00 | Vacuum Tube (Dual Triode) | dual triode | 1S1 • 2A61 • 3A8 • 3L5 • W |