Members of the Nashoba Valley Amateur Radio Club have documented an extensive project they undertook to build sets of band pass transmitting filters for reducing the interference between HF transceivers operated in close proximity.
The “Ugly” Filter web article describes various aspects of building the filters and traces the thoughts of the team that came up with the project and designed the filters. NVARC has used these filters since 2005 in field day and they have performed very well. The club has generously made the plans available for anyone that may wish to build the filters.