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