90515 Frequency Calibration Unit
| In the 1950's more-and-more commercial FM broadcast station were appearing on the 88-108MHz band or at that time what was called the High FM Band. Millen was right there to provide this 90515 Frequency Calibration Unit to assist the station engineers with meeting the rigid transmit frequency requirements set forth by the FCC. The 90515 is actually a combined package of their already existent 9050X series Secondary Frequency Stardard with the newly created 90511 Frequency Multiplier and Mixer, This multiplier unit consists of two double-function 6J6 tubes, both of which are used as double multipliers to obtain an output of 81MHz. This output is mixed with a sample of the transmitters output by means of a 1N34 diode. Tuning of the multiplier stages is fixed, whereas tuning the mixer stage is brought out to the front panel. The 90511 multiplier/mixer unit could be purchased separately, but it came in the larger size cabinet with room to install the 9050X series Secondary Frequency Standards. Once together they become the 90515. Owner: Don Buska, N9OO Submitted: 17-February-2023 |