1401: Difference between revisions

1401 (view source)

Revision as of 20:28, 14 October 2014

1,069 bytes added , 14 October 2014

rf operation

Jimnarem

133

edits

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 but the later versions are 100, 100, and 10 KHz.  There is also a 1401A-1
 which has a 75 ohm input impedance.  The predecessor 1401 did not have
-the calibrator out or pushbutton switch.
+the BNC "cal output" or "cal on" pushbutton switch.
 The 1401A is designed to be used with an oscilloscope with 10 horizontal
-divisions and 6 vertical divisions.  Note that most full sized Tektronix
+divisions and 6 vertical divisions.  Tektronix says it is compatible with any
+oscilloscope having 0.5V/div horizontal deflection factor and 1.2V full screen
+vertical deflection.  Note that most full sized Tektronix
 oscilloscopes have 8 vertical divisions so use care when doing the
-initial setup and reading the scale in dBm.
+initial setup and reading the scale in dBm.  Also note the lack of a Z-axis
+output.
+Operation is typical of a swept front end analyzer.  The input is attenuated and
+low-pass filtered to 500 MHz.  It is then mixed with the first LO, a variactor
+tuned oscillator that can sweep 695 MHz to 1195 MHz.  The first mixer is a double
+balanced, four diode star.  The signal is DC coupled to this mixer.  The manual is
+not clear as to the damage level; with no attenuation they say that it is non linear
+above -30 dBm.  The first IF output is 695 MHz, filtered to remove the other image.
+The first IF is mixed with a 720 MHz fixed 2nd LO to produce the 2nd IF at 25 MHz.
+The 25 MHz 2nd IF leaves the shielded RF housing and enters the IF board via SMB connector P210.
+This 2nd IF is then amplified and mixed with a 30 MHz fixed 3rd LO to produce the
+rd IF of 5 MHz.  This 3rd IF is then passed through the selectable RBW filters,
+detected and send to the video out.
 See TekScope January 1972 pages 14-15 for some servicing notes that