Sorry I'm sitting in a day long meeting with only a cell phone. The W3NQN high pass and band pass filters work well and use 7 parts. There is something else called a “brick wall AM” filter that was built by a guy in texas but i dont know much about it.
Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ
Owner - Operator
Big Signal Ranch – K9ZC
Owner – Operator
Villa Grand Piton - J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com
“If you search the QST archives for his call”
not exactly details but helpful, with the $5 claim, I thought you might have something specific in mind
was it the feb 1978 bc band energy-a rejection filter
Alternative Filter Design