Use this site to render the horizon panorama from any place on earth. – http://www.heywhatsthat.com/

Create an account and create antenna coverage plots here: http://www.cplus.org/rmw/rmonline.html

Very good explanation of the sun and HF radio propagation: http://www.hamradioschool.com/sunspots-and-propagation/

Coax loss calculator: http://arrg.us/pages/Loss-Calc.htm

Great site w many topics covered- baluns, antennas, etc: http://vk5ajl.com/info/info.php

Mag loop antenna info and links: http://www.aa5tb.com/loop.html

Another good mag loop info source: https://www.nonstopsystems.com/radio/frank_radio_antenna_magloop.htm

Ferrite vs air choke data (mixes and coax types are silly but principle is point): http://www.karinya.net/g3txq/chokes/

Faraday cage info: https://www.gamry.com/application-notes/instrumentation/faraday-cage/

SATELLITE RELATED:

Site w real time APRS info heard from the ISS (use it to see if you make it in etc!): http://www.ariss.net/index2.cgi

 

Misc and random- 

Motorola Micor squelch explained: http://www.repeater-builder.com/micor/micor-bi-level-squelch-theory.html