Yaesu FTdx5000MP: Filtering Out QRM 2kHz Away

Описание: I was listening to a 40m net and a great opportunity presented itself. Some strong stations started talking 2kHz below the net frequency. This provided a challenge for the filters and DSP to go to work. I’m listening with my Yaesu FTdx5000MP in this video, but most of what I show can be accomplished with other state-of-the-art transceivers. The *mu-tuning variable preselector is the exception. Most other radios do not include a variable (narrow bandpass) preselector. The *mu-tuning preselector is optional but the FTdx5000MP includes a built-in (less narrow) variable preselector called VRF (Variable RF). VRF is still quite effective but the external mu-tuning preselector is even more narrow that the VRF preselector.

These “variable preselectors” are high-Q factor (+300) filters that are inserted into the receiver signal chain between the attenuation stage and the bandpass filter stage. They narrow down the amount of RF spectrum allowed to continue to the bandpass filter stage to a mere few dozen kHz, by motor-driving a large 1.1” (28 mm) ferrite
core stack through a 2” high (50 mm) coil structure.

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