Roofing Filter Design

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

Roofing filter design.

The term roofing stems from the fact that it protects the rest of the radio following it from out of the passband signals. Kenwood ts 950 series roofing filters. There are two basic designs for modern radios. The amplifier provides enough gain to override the filter insertion loss.

The imd dynamic range will be improved 5 to 15 db for some signal spacings. 250 hz 500 hz or 1 8 khz for ssb would be acceptable values. First filter as close to the antenna as possible 1 st if typical why. 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.

Roofing filters are usually crystal or ceramic filter types. Using a more narrow roofing filter can eliminate this unwanted signal and eliminate the agc pumping. A close up of the roofing filter section of the frontend board. It is usually placed as clos e to the first mixer as possible in order to be effective.

To reduce the amount of rain falling on the roof a more narrow roofing filter is required. Sized to pass the widest mode of operation improve dr3 begins with. 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. To the left is the 2x 4 pole ssb filter to the right is the 2x 3 pole cw filter.

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.