Daily Archives: October 23, 2020

People may be confused by the fact that the RSP family have software selectable notch filters to attenuate the main broadcast bands (AM, FM, DAB) and may overlook the other notch filters available in SDRuno.  These are the extremely versatile programmable passband notch filters which are ideal for removing co-channel interference in crowded AM bands.

The details (reproduced here) are all on page 55 of the current edition of the SDRuno user manual:  https://www.sdrplay.com/docs/SDRplay_SDRuno_User_Manual.pdf

Each VRX offers four notch filters to suppress unwanted signals, placed before the audio AGC. Each notch filter can be enabled/disabled by the relevant button in the RX Control panel. The notch filters bandwidth & frequency settings are available in the RX EX Control panel. For notch filters 1 & 2 the frequencies can be quickly set “on the fly” as follows:

– Place the cursor in the spectrum part of the Aux Spectrum panel (SP2); press and hold the SHIFT key: a yellow vertical line will be shown at cursor position.
– Move the above line next to the signal you wish to suppress.
– Assign that frequency to Notch 1 by Left-Click or Notch 2 by Right-Click.
– Release the SHIFT key.
– For each enabled notch the relative frequency is marked in the spectrum by a dotted vertical line, light-blue for Notch 1 and light-pink for Notch 2.

The NCHL button in the RX Control panel enable/disable the notch-lock feature. When notch-lock is active, the notch filters frequencies remain fixed when the VFO is changed until the notch frequency relative to the VFO is outside of the SP2 displayed bandwidth.

See this video demonstration of the notch filters in action with real signals: