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One other, relatively minor, shortcoming of the Philco 7008 is that it doesn't use Post-Marker Injection as the B&K 415 and the similar Heathkit unit for 44 MHz IF do. Post-Marker systems insert the marker(s) into the display AFTER the sweep signal passes through the IF stages under test, so that the marker "pips" appear on the display without the marker frequencies actually being injected into the circuitry under test. Only the SWEEP signal passes through the Generator cable into the TV circuitry and the MARKER insertion occurs between the Probe and the Vertical Input of the Scope. This shortcoming of the Philco 7008 makes it somewhat more tricky to avoid distortion of the response curve caused by marker injection. I am not aware of any self-contained Post-Marker type units for the older 22-24 MHz system, however, RCA manufactured a Marker Adder for use with external generators and scope which did actually produce a Post-Marker sweep. Unfortunately, its use of multiple individual instruments and the resultant interconnections which were required represented another potential source of distortion.
Is anyone aware of a self-contained Post-Marker instrument which supports the older IF systems?
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