Monthly Archives: May 2017

Always forward.

I haven’t forgotten of my little corner of the internet.  Things are busy.  I’ve constructed two band pass filters based on the article here:

http://www.arrl.org/files/file/Technology/tis/info/pdf/8809017.pdf

…and cribbing notes from a QRPSchool video:

http://qrpschool.com/portable-ops/band-pass-filters-for-qrm/

BLUF – mine don’t work.

My first, immediate observation, is that trying to get 48 turns on a T-48 core is a goddamn no-go.  I found an online calculator and re-ran the numbers on a larger toroid.  Pictures of my failed attempts may be posted at a later time.  Additional observations from the EE I had check my work:

The metal project box may act like a faraday cage.  RF is like voodoo, and my plastic boxes may not provide enough isolation.

My boxes were built according to the schematic in the article.  The actual filters are constructed differently – maybe.  All the L1 components share the same positive and ground connection.

My next attempt will be as close to exact duplication as possible, metal enclosure and foil PCB.