“Choosing A Ham Radio” is a supplement to the Ham Radio License Manual you can download as a PDF guide for this important first step.

Modulation

• Wikipedia entry on Modulation - a comprehensive review of modulation

AM

• ARRL Technical Information Service - plenty of articles and links about AM
  
• AMfone - a Web site about AM operating on the HF bands  

SSB

• Wikipedia entry on Single Sideband - in-depth treatment with the theory

FM / PM

• Understanding FM Transmitters - a QST article about FM
  
• Wikipedia entry on Frequency Modulation - in-depth treatment with the theory

CW and Morse Code

• The ARRL's online resources for learning about CW and Morse code
• FISTS - an organization devoted to helping you learn to use CW
• Morse Code Operating for Amateur Radio is an ARRL book about learning and using CW

Signal bandwidths – the typical bandwidths listed in Table 2-3 are approximate maximum bandwidths occupied by a signal.  Actual signals can be narrower. Wider spacing may be required for an acceptable level of interference depending on the receiver bandwidth.  For example, a perfect CW signal occupies 0 Hz of bandwidth, but practical transmitters add noise and other signal artifacts so that the resulting signal occupies about 150 Hz of spectrum (the generally agreed on maximum as covered by question T8A11) and an adjacent receiving station may need to be separated by 100 to 300 Hz.

The squelch function is discussed more completely in the supplement “Choosing A Ham Radio” listed at the start of this web page.

Instead of a separate device, many digital modes use the sound card built in to all recent computers to connect them to a radio.  The article introducing the digital mode PSK31 illustrates the typical use of a sound card for this purpose.

The four-part series of articles about digital modes will provide lots of background information about these popular forms of digital communication used by hams.  You can find more information about using digital modes at:

Winlink - organization that has developed and maintains the worldwide ham radio email network.
APRS - the home page of the Automatic Position Reporting System
TAPR - sponsor and organizer of digital communications initiatives

And in this print reference, Get on the Air with HF Digital by ARRL Publications Manager, Steve Ford, WB8IMY

You’ll want to be sure you understand the FCC’s Part 97 rules (Part 97.113 – Prohibited Transmissions) on commercial content and use of Amateur Radio.

If you’re interested in operating from a vehicle, be sure to bookmark KØBG’s web page on Mobile Amateur Radio.  Alan is an enthusiastic and prolific author on the subject.

Given the interest in emergency and disaster-preparedness, there are a lot of on-line resources on this and related topics.  Start with the How Stuff Works pages on generators and inverters.

A comprehensive website on the subject, Battery University is a resource for many questions about batteries.  In addition, the ARRL Technical Information Service page on batteries has several ham-specific articles and links to more battery resources.