7L12: Difference between revisions

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The 7L12 is a traditional triple-mixing spectrum analyzer design. The input signal runs through a step attenuator (0 to 60 dB in 10 dB steps), a 1.8 GHz low-pass filter and a 3 dB pad (to isolate the mixer from LPF reflections) to a 1st mixer. The 1st LO is a YIG oscillator running at 2.095 GHz to 3.9 GHz, resulting in a 2.095 GHz 1st IF. This IF passes through a "traveling wave damper" (isolator), a 2.2 GHz LPF and a 10 MHz wide 2.095 GHz bandpass filter before reaching the 2nd mixer. The 2nd LO oscillates at 2.2 GHz (variable by +/- 1 MHz) for a 2nd IF of 105 MHz, which is amplified, then filtered in a 3-stage helical filter with 3 MHz bandwidth before passing through a 3rd mixer to the final 10 MHz IF, variable resolution filters, and post-resolution amplifier to the "Function IF amplifier" that implements the linear or logarithmic detector.

A phase lock circuit controls the 1st LO at spans of 0.1 MHz/Div and less, tying its frequency to a multiple of 2.21 MHz using ~~an avalanche pulse shaper driven~~ diode sampler as a mixer. In phase lock, the 2nd LO is swept instead of the 1st. The fine frequency control is only operational in phase lock mode.

A phase lock circuit controls the 1st LO at spans of 0.1 MHz/Div and less, tying its frequency to a multiple of 2.21 MHz using a diode sampler employed as a mixer. The sampling gate is driven by an avalanche pulser. In phase lock, the 2nd LO is swept instead of the 1st. The fine frequency control is only operational in phase lock mode, one of the key limitations of this design.

The 7L12 includes a standard sweep circuit built around the [[155-0056-00]] Sweep Control (U1140) and [[155-0042-02]] (U1160) Miller Integrator custom ICs. The 7L12 also uses the TEK-custom quad opamp [[155-0035-00]] in several places.

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 The 7L12 is a traditional triple-mixing spectrum analyzer design.  The input signal runs through a step attenuator (0 to 60 dB in 10 dB steps), a 1.8 GHz low-pass filter and a 3 dB pad (to isolate the mixer from LPF reflections) to a 1<sup>st</sup> mixer.  The 1<sup>st</sup> LO is a YIG oscillator running at 2.095 GHz to 3.9 GHz, resulting in a 2.095 GHz 1<sup>st</sup> IF.  This IF passes through a "traveling wave damper" (isolator), a 2.2 GHz LPF and a 10 MHz wide 2.095 GHz bandpass filter before reaching the 2<sup>nd</sup> mixer.  The 2<sup>nd</sup> LO oscillates at 2.2 GHz (variable by +/- 1 MHz) for a 2<sup>nd</sup> IF of 105 MHz, which is amplified, then filtered in a 3-stage helical filter with 3 MHz bandwidth before passing through a 3<sup>rd</sup> mixer to the final 10 MHz IF, variable resolution filters, and post-resolution amplifier to the "Function IF amplifier" that implements the linear or logarithmic detector.
-A phase lock circuit controls the 1<sup>st</sup> LO at spans of 0.1 MHz/Div and less, tying its frequency to a multiple of 2.21 MHz using an avalanche pulse shaper driven diode sampler as a mixer.  In phase lock, the 2<sup>nd</sup> LO is swept instead of the 1<sup>st</sup>.  The fine frequency control is only operational in phase lock mode.
+A phase lock circuit controls the 1<sup>st</sup> LO at spans of 0.1 MHz/Div and less, tying its frequency to a multiple of 2.21 MHz using a diode sampler employed as a mixer.  The sampling gate is driven by an avalanche pulser.  In phase lock, the 2<sup>nd</sup> LO is swept instead of the 1<sup>st</sup>.  The fine frequency control is only operational in phase lock mode, one of the key limitations of this design.
 The 7L12 includes a standard sweep circuit built around the [[155-0056-00]] Sweep Control (U1140) and [[155-0042-02]] (U1160) Miller Integrator custom ICs.  The 7L12 also uses the TEK-custom quad opamp [[155-0035-00]] in several places.

7L12: Difference between revisions

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