|
Here's my Alignment bench. For 21 MHz IF, I use an Eico 369 to which I've added a front-panel jack which performs double duty as an External Marker input or as a Marker Output to my Elenco 9500 (Marker Generator / Frequency Counter combo unit), connected to a LabVolt 10 MHz scope with a 5" CRT. For bias supplies, I fire up the B&K 415 to use its built-in supplies. For 41 MHz IF work, I use the B&K 415 (crystal-controlled markers, no need for a Counter except during annual Calibration check-ups) and B&K 5 MHz scope with 3" CRT. Everything is pre-wired on the bench for maximum efficiency. The Tektronix 547 is my main scope (DC to 50 MHz) for waveform analysis, but I also have a Tektronix 475A (DC to 250 MHz) on the shelf for applications requiring an extremely wideband instrument. The Ext. Mkr. jack was standard on the Eico 368 (which didn't use post-marker injection), but Eico didn't include the Ext. Mkr. jack on the 369 with its post-marker circuitry. Both Eico units achieve their Sweep function by applying a 60 Hz sinewave to the control winding of a saturable reactor, thus varying the inductance in the Sweep oscillator circuit at a 60 Hz rate and proportional to the amplitude of the 60 Hz sweep waveform. With the Sweep Width control set to minimum, a small DC bias current through the control winding establishes a fixed inductance approximately centered between the maximum and minimum values which occur at the corresponding peaks of each cycle of the control waveform at maximum Sweep Width control setting. The saturable reactor method produces Sweep without any wear-prone moving parts, unlike other generators such as the Precision E-400, Philco 7008, Hickok 610, etc. which use a mechanical device resembling a small loudspeaker to vary reactance in their Sweep oscillator circuits by mechanically flexing one of the inductive or capacitive elements of its tuned circuit to vary the output frequency above and below the center frequency determined by the dial setting.
|