1L20
The Tektronix 1L20 is a spectrum analyzer plug-in for 500-series scopes. It covers the frequency range from 10 MHz to 4.2 GHz.
The 1L20 was originally the third-party Pentrix L-20. The model number was changed some time after Tektronix took over Pentrix in 1964.
Key Specifications
| Frequency range | 10 MHz to 4 GHz |
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| Sensitivity | −110 to −90 dBm |
| Dispersion | 15 kHz to 60 MHz, magnifier usable to 2.5 kHz |
| Resolution bandwidth | 1 kHz to 100 kHz, variable |
| Display | log, lin, square, video |
Prices
$1,995 in 1965 ($19,400 in 2023 dollars)
Internals
Originally (in SN 100-519), the UHF oscillator tubes V40 and V41 were type Y1506 (Tek part #154-0499-00). As the Y1506's became unavailable, a 1967 revision of the 1L20 changed these to Y1641 (GE 16411?) tubes (154-0506-00), necessitating a slight modification of their DC filament supply circuit.
Pictures
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Front
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Left
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Right
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Top
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Bottom
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Block Diagram
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RF and Phase Lock Block Diagram
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IF Block Diagram
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RF Section
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Phase Lock Circuit
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Wideband Amp and Mixer
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Sweeper
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IF Attenuator
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IF Amp, 70 MHz Oscillator and Mixer
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Variable Resolution Circuit
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Output Amplifier
Components
Some Parts Used in the 1L20
| Part | Part Number(s) | Class | Description | Used in |
|---|---|---|---|---|
| 12AU6 | 154-0040-00 | Vacuum Tube (Pentode) | RF pentode | 81 • 112 • 1L10 • 1L20 • 1L60 • 3L10 • 512 • 556 • 575 • 545 • 547 • 549 • 581 • 585 • A • B • C • G • K • H • L • ML • M • N • O • R • S • Z |
| Y1506 | 154-0499-00 | Vacuum Tube (Triode) | SHF cermet triode | 1L20 |
| Y1641 | 154-0506-00 • 154-0510-00 | Vacuum Tube (Triode) | SHF cermet triode | 1L20 • 491 |