Roofing Filter Design

Protects following circuits from nonlinear operation due to strong out of band signals what.

Roofing filter design.

For more demanding uses like listening to weak cw or ssb signals a roofing filter is required that gives a smaller passband appropriate to the reception mode in use. It is usually placed as clos e to the first mixer as possible in order to be effective. The imd dynamic range will be improved 5 to 15 db for some signal spacings. Note the shield to improve the stop band beyond 100db and the small trimmers needed to align the cw filter to center exactly on 9 000000mhz.

A close up of the roofing filter section of the frontend board. Mcf or discrete crystal construction width. These allow a much better filtering curve than a roofing filter which often uses a high first if above 40 mhz. Think of the roofing filter as a roof on a house the wide filter allows the dsp and hardware agc to respond to all the rain falling on the roof.

Basically a roofing filter is simply the first if filter in a radio. The term roofing stems from the fact that it protects the rest of the radio following it from out of the passband signals. Roofing filter basics where. First filter as close to the antenna as possible 1 st if typical why.

Kenwood ts 950 series roofing filters. Roofing filters are usually crystal or ceramic filter types. 250 hz 500 hz or 1 8 khz for ssb would be acceptable values. Using a more narrow roofing filter can eliminate this unwanted signal and eliminate the agc pumping.

To reduce the amount of rain falling on the roof a more narrow roofing filter is required. The ts 950 roofing filter mod consists of a 6 pole 4 to 5 khz wide filter followed by a high dynamic range feedback amplifier. Sized to pass the widest mode of operation improve dr3 begins with.