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Showing posts from February, 2009

RFFE1 Why you may (or may not) need it

RFFE stands for "Radio Frequency Front End" and the "1" stands for the first version (0-62.5 MHz coverage).

When I was designing the QS1R board, I had to decide whether to include bandpass filtering and RF amplification on the board. In fact the initial prototypes "RevA" included RF amplification on the QS1R board. Unlike another DDC based direct sampling receiver "Perseus", QS1R was designed to be more than a SW receiver. In addition to a SW receiver, QS1R was meant to facilitate experimentation in the RF spectrum up to at least 300 MHz. I finally settled on a 55 MHz low pass filter (which can be bypassed) and no active components in front of the ADC on QS1R. Any active devices, bandpass filters, or attenuation would be added by a separate board such as the RFFE1.

The antenna that I use for my QS1R is a center fed, non-resonant dipole at 50 feet. The total wire length is about 240 feet with only about 100 feet of that running horizontally…