How To Use Roofing Filters

There are two basic designs for modern radios.

How to use roofing filters.

250 hz 500 hz or 1 8 khz for ssb would be acceptable values. Using merv 5 8 filters will keep your hvac system more efficient than using higher rated filters as long as you replace your filters regularly. If the agc cannot see or hear signals nearby in the passband it does not need to use part of its resources to attempt to deal with it. These narrow filters require that the receiver uses a first if well below vhf range perhaps 9 or 11 mhz.

If your family has health or allergy issues then you may want to look for a high efficiency filter that s merv 11 or. If you are susceptible to allergies asthma or other respiratory conditions then you may want to use a filter with a merv rating of about 9 to 12. The roofing filter makes the passband seen by the agc much less narrower and in doing so the weak station is not minimized because of the presence of the strong station nearby. The top of the board should be just below the top of the shield on the pa unit.

A basic merv 4 filter will likely be the cheapest but won t catch certain small particles like dust mites and pet dander that could be in your home. The degree of contamination will depend on several things including the length of time since the last rainfall proximity of the catchment. 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. Align one of the standoffs to be in th panel on the pa unit.

Basically a roofing filter is simply the first if filter in a radio. The use of roof washers and roof water filters can reduce the amount of these contaminants entering the system. The first water to come off the roof at the beginning of a rainstorm is the most contaminated. The term roofing stems from the fact that it protects the rest of the radio following it from out of the passband signals.

Position the roofing filter in place temporarily as shown in figure 2. For residential furnaces filters range from 4 to 12 on the merv scale. 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. It is usually placed as clos e to the first mixer as possible in order to be effective.