Roofing Filter Design

The amplifier provides enough gain to override the filter insertion loss.

Roofing filter design.

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

First filter as close to the antenna as possible 1 st if typical why. Sized to pass the widest mode of operation improve dr3 begins with. Roofing filter basics where. These allow a much better filtering curve than a roofing filter which often uses a high first if above 40 mhz.

The imd dynamic range will be improved 5 to 15 db for some signal spacings. 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. 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. There are two basic designs for modern radios.

To the left is the 2x 4 pole ssb filter to the right is the 2x 3 pole cw filter. 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. 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. A close up of the roofing filter section of the frontend board. Protects following circuits from nonlinear operation due to strong out of band signals what.