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7L18 (view source)

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[[Image:7L18-front.jpg|600px|center]]
{{Plugin Sidebar
The Tektronix 7L18 is a spectrum analyzer plug-in [[introduced in 1978]] for [[7000-series scopes]].
|manufacturer=Tektronix
|series=7000-series scopes
|type=7L18
|summary=18 (60) GHz Spectrum Analyzer
|image=7L18-front.jpg
|caption=Tektronix 7L18
|introduced=1978
|discontinued=1984
|designers=Linley Gumm;
|manuals=
* [[Media:070-2339-02.pdf|7L18 Operators Manual]] (OCR)
* [[Media:061-1469-02.pdf|7L18 Interim Service Manual]] (OCR)
* [[Media:Tek tracking the wild preselector 7L18.pdf|Tracking the Wild Preselector in Its Native Habitat - The 7L18]]
* [[Media:Tek 7L18 Opt1.pdf|Digital Interfacing for the 7L18]]
}}
The '''Tektronix 7L18''' is a spectrum analyzer plug-in [[introduced in 1978]] for [[7000-series scopes]].
It occupies three plug-in bays in the oscilloscope.
It occupies three plug-in bays in the oscilloscope.
It covers the range from 1.5 GHz to 18 GHz with the internal mixer and 12.5 GHz to 60 GHz
using external mixers.
Note that it will NOT do 1.5 to 18 in one span, it will only max span
the range selected by the BAND/HARMONIC control.
This range is determined by the hetrodyne harmonic number and sign (sideband) and
the range of the first LO, which is 2 GHz to 4 GHz.


The input attenuator range is 0 dB to 60 dB in 10 dB steps and is a standard Wenschel Engineering
{{BeginSpecs}}
product driven by a belt.  The range is encoded for the digital dBm reference level display.
{{Spec | Frequency range      | 1.5 GHz to 18 GHz with the internal mixer, 12.5 GHz to 60 GHz using external mixers }}
The signal then passes through a YIG preselector filter with a 50 MHz bandwidth.
{{Spec | Frequency span      | 0; 200 Hz/Div to 500 MHz/Div in 1−2−5 steps; Max (see note below) }}
{{Spec | Resolution bandwidth | 30 Hz to 3 MHz in decade steps}}
{{Spec | Vertical scale      | 10 dB/Div, 2 dB/Div, or linear }}
{{Spec | Input attenuator    |  0 dB to 60 dB in 10 dB steps }}
{{Spec | Sweep                | 1 μs/Div to 20 s/Div, auto, ext, or manual }}
{{Spec | Digital functions    | two memory banks (A, B); Display A, B - A saved, peak hold }}
{{EndSpecs}}
''Please expand '' [[Category:Specifications needed]]
 
==Context==
[[Linley Gumm]] says:
<blockquote>Another disappointment was the 7L18 microwave analyzer project, one of the earliest Tek products to have a microprocessor in it.
 
"We started work on developing this product in 1974, and finally shipped our first instrument in 1978.
As I look back, it was a terribly crude microprocessor, and we made every error in the book.
Of course, we didn't have any of the tools that are available today."
 
Although the 7L18 never did sell well, Linley and his crew developed components and technologies that later were used in the [[492]].
([[Media:LinleyGumm_TW_03271987.pdf|TekWeek March 27, 1987]])
</blockquote>
 
==Internals==
The LO is a YIG tuned oscillator covering the 2 GHz to 4 GHz range. 
Its output passes through a sampler assembly used to PLL the YIG on small resolution bandwidths.
The output of the sampler goes to the LO input on the mixer.  The mixer IF output is 510 MHz.
 
The 7L18's components are controlled by an [[Intel 4004]] 4-bit microprocessor.
 
The 7L18 will NOT do 1.5 GHz to 18 GHz in one span, it will only max span the range selected by the BAND/HARMONIC control. This range is determined by the heterodyne harmonic number and sign (sideband) and the range of the first LO, which is 2 GHz to 4 GHz.
 
The input attenuator is a standard Weinschel Engineering product driven by a belt.   
The range is encoded for the digital dBm reference level display.
The signal then passes through a YIG preselector filter with a 50 MHz bandwidth.
After the YIG filter, the signal enters the RF input of the mixer assembly.
After the YIG filter, the signal enters the RF input of the mixer assembly.


The LO is a YIG tuned oscillator covering the 2 GHz to 4 GHz range. It's output passes
==Links==
through a sampler assembly used to PLL the YIG on small resolution bandwidths.
* [[Media:Tekscope 1977 V9 N3.pdf  | TekScope Vol. 9 No. 3, 1977]]
The output of the sampler goes to the LO input on the mixer. The mixer IF output
* [http://w140.com/tektronix_spectrum_analysis_using_waveguide_mixers.pdf Spectrum Analysis Using Waveguide Mixers (PDF)]
is 510 MHz.
* [[016-0631-01|Waveguide Mixers for 492 and 7L18]]
 
==Pictures==
<gallery>
Tek 7l18 3822 1.jpg
Tek 7l18 3822 2.jpg
Tek 7l18 3822 3.jpg
Tek 7l18 3822 4.jpg
Tek 7l18 3822 5.jpg
Tek 7l18 3822 6.jpg
Tek 7l18 3822 7.jpg
Tek 7l18 3822 8.jpg
Tek 7l18 3822 9.jpg
Tek 7l18 3822 10.jpg
Tek 7l18 3822 11.jpg
Tek 7l18 3822 12.jpg
</gallery>
Service views:
<gallery>
7L18-top.jpg|Top view
7L18-bottom.jpg|Bottom view
7L18-service-rightfront.jpg|Service setup for the right front panel
</gallery>
 
Boards within the digital card cage (from back to front):
<gallery>
7L18-board-crtreadout.jpg|CRT Readout board
7L18-board-centerfreqreadout.jpg|Center Freq Readout board
7L18-board-sweephoriz.jpg|Sweep Horiz board
7L18-board-spanatten.jpg|Span Atten board
7L18-board-phaselock-rear.jpg|Phase Lock module, rear
7L18-board-phaselock-front.jpg|Phase Lock module, front
7L18-board-phaselocklogicctl.jpg|Phase Lock Logic CTL
7L18-board-vrnoisefilter.jpg|VR Noise Filter
7L18-board-logvideoamp.jpg|Log & Video Amp
7L18-board-centerfreqdvm.jpg|Center Freq DVM
7L18-board-centerfreqdvm-front.jpg|Digital Storage, front
7L18-board-centerfreqdvm-back.jpg|Digital Storage, back
7L18-board-microcomputer.jpg|Micro Computer
</gallery>


[[List of manuals that are needed|Manual needed]] (with schematics).
The microcomputer board is built using three very old Intel chips:  an Intel 4004 processor,
an Intel 4002 320-bit RAM and 4-bit output port, and an Intel D4289 standard memory
interface.  The D4289 connects the 4004 to the two 2K8 ROMs.  Note that in an earlier
version of the 7L18 there were 6 ROMs.


Internal views of the analog parts:
<gallery>
<gallery>
Image:7L18-sampler.jpg|Internal of the LO sampler
7L18-sampler.jpg|Internal of the LO sampler
Image:7L18-top.jpg|Top view
</gallery>
</gallery>
{{Custom ICs|7L18}}
[[Category:7000 series combined plugins]]
[[Category:Spectrum analyzers]]
[[Category:Specifications needed]]
Retrieved from "https://w140.com/tekwiki/wiki/Special:MobileDiff/7509...81308"

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