Electronics
  
 
http://www.learnelectronicsonline.com
http://components.about.com/od/Theory/
http://www.falstad.com/circuit
https://www.partsim.com
http://www.falstad.com/circuit
http://www.electronics2000.co.uk/calc/

 
https://kicp.uchicago.edu/education/explorers/2002summer-YERKES/pdfs-sum02/background.pdf
http://scitoys.com/scitoys/scitoys/radio/radio.html
http://boyslife.org/search/?q=amateur+radio#gsc.tab=0&gsc.q=amateur%20radio&gsc.page=1
https://sites.google.com/a/ztlearn.com/wrh/radio-kids/ar-wiki.png
http://www.hamradioschool.com/category/current_articles/shack_talk







http://www.oldradio.com