About 15 years ago I built a switchable front end crystal filter, I was going to market it but it was too expensive for the Ham market. It covers 1800 to 1850 in 5kHz segments with a slight overlap so that there are no gaps, each section is a half lattice, the insertion loss is about 6dB but that isn't a problem because I always have about -15dB of attenuation in the receive path input. Nose bandwidth is 5kHz and about 8kHz at -20dB. Lack of noise blanker performance is not a problem because big signals make the blanker useless anyway. I used it during contests when my rig was an IC781, since changing to a more modern rig, an IC7851, the filter provides no significant improvement. For working DX on a crowded band it is useful if your rig does not have a good roofing filter.
HNY /MX Dave AA0RS _________________ Topband Reflector Archives - http://www.contesting.com/_topband