Roofing Filter Design

First filter as close to the antenna as possible 1 st if typical why.

Roofing filter design.

The amplifier provides enough gain to override the filter insertion loss. 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. 250 hz 500 hz or 1 8 khz for ssb would be acceptable values. Protects following circuits from nonlinear operation due to strong out of band signals what.

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. There are two basic designs for modern radios. Mcf or discrete crystal construction width. Sized to pass the widest mode of operation improve dr3 begins with.

Roofing filter basics where. Using a more narrow roofing filter can eliminate this unwanted signal and eliminate the agc pumping. Kenwood ts 950 series roofing filters. To reduce the amount of rain falling on the roof a more narrow roofing filter is required.

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. Roofing filters are usually crystal or ceramic filter types. A close up of the roofing filter section of the frontend board. 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.

The imd dynamic range will be improved 5 to 15 db for some signal spacings. To the left is the 2x 4 pole ssb filter to the right is the 2x 3 pole cw filter. Basically a roofing filter is simply the first if filter in a radio.