Two unrelated questions: A recent improvement to my station has brought other issues to the forefront. I am going to need a serious filter to keep AM BC stations out of my preamp. I had been thinking bandpass filters, but none I am aware of roll off quickly enough below 1.8 MHz. I am now investigating high pass filters. The W3NQN filters sold by Array Solutions look very impressive. Is there anything else (maybe a little cheaper) anywhere near this or are these in a class by themselves? This will be a receive only application.
I am also looking for a better formula for calculating inductance of single layer air core coils. Although I have done well enough over the years with the "simplified formula" from ARRL Handbooks which gives a "close approximation" I now wish for something better. Ideally I would like something accurate for coils of any length to diameter ratio, including very short coils. A free downloadable or online calculator would be great, but a plain old formula is fine too. I have found several on the internet but which ones to trust? Any guidance would be appreciated. Thanks, 73, & HNY! Paul N1BUG _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
