What is the loss through the roofing filters and is it compensated for?
Like other roofing filters, the narrower the passband, the more loss. In general the loss is similar to those shown for the FT-1000 8.215 MHz filters shown on the INRAD web site. Our 5 pole filters in some cases have a little less loss. The loss at this point in the radio (the first IF) has very little impact on MDS or other characteristics, because the noise figure is established in earlier stages. When you install any roofing filter, you use the menu to tell the firmware what the filter’s bandwidth is, any small offset from 8.215 MHz, and what the relative loss of the filter is. The DSP adjusts the 15-kHz IF gain based on the entered loss amount, so all filters have the same overall gain. Once a filter is installed, you can specify which modes it is available in (or all modes).
Like other roofing filters, the narrower the passband, the more loss. In general the loss is similar to those shown for the FT-1000 8.215 MHz filters shown on the INRAD web site. Our 5 pole filters in some cases have a little less loss. The loss at this point in the radio (the first IF) has very little impact on MDS or other characteristics, because the noise figure is established in earlier stages. When you install any roofing filter, you use the menu to tell the firmware what the filter’s bandwidth is, any small offset from 8.215 MHz, and what the relative loss of the filter is. The DSP adjusts the 15-kHz IF gain based on the entered loss amount, so all filters have the same net overall IF gain. Once a filter is installed, you can specify which modes it is available in (or all modes).
