10. Operating on the Air on The HamStudy Amateur Extra Class HamBook (2024 - 2028)

10.1 DX and Contest Contacts

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.1: DX and Contest Contacts #

When a rare DX station comes on the air, dozens or even hundreds of operators may call it at once. Working that pileup takes the same routine as a contest contact: listen first, call when the station is listening, and send the exchange the rules require. The contact itself may last seconds, but it sits between two other jobs. Before calling, you need to find the activity. Afterward, the log goes to the contest sponsor, and the contact may still need confirming for an award.

10.2 Choosing a Digital Mode

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.2: Choosing a Digital Mode #

An FT8 contact can finish without either operator typing a word. PSK31 carries a typed conversation, a Winlink session over PACTOR can deliver an email with a photo attached, and WSPR holds no conversation at all. Each mode serves a particular job, and the job decides what the mode gives up: speed, bandwidth, or the ability to get through noise.

Intended use	Typical modes
Keyboard conversation	RTTY, PSK31, MFSK16
Reliable data and file transfer	PACTOR
Short messages in timed periods	FT8, FT4, FST4
Propagation reporting	WSPR

Getting Data into the Transmitter #

Most of these HF modes shift among tones, which makes them forms of frequency-shift keying. A radio can make those shifts in two ways. In one, a keying line from the computer shifts the radio’s own oscillator. In the other, the computer’s audio interface generates the tones, and the SSB transmitter translates them to RF. If you’ve run FT8, you’ve used the second.

10.3 Meteor Scatter and Moonbounce

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.3: Meteor Scatter and Moonbounce #

Section 7.4 introduced two unusual paths, each stingy in its own way. A meteor trail lasts only a moment. The Moon stays in view for hours but returns only a tiny part of the energy sent to it. Each path calls for its own kind of digital mode: one fits a complete message into a fleeting opening, and the other recovers a message from deep noise.

10.4 Satellite Orbits and Links

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.4: Satellite Orbits and Links #

A satellite in low Earth orbit circles the planet in about 100 minutes, so each pass across your sky usually lasts 15 minutes or less. Fitting a contact into that window takes planning; the satellite won’t wait while you find it. You need to know when and where the satellite will appear, which bands it uses and which you may transmit on, and how to keep its signal from fading.

10.5 Satellite Signals and Control

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.5: Satellite Signals and Control #

An FM satellite works like a repeater in the sky: one channel up, one channel down, and one conversation at a time. A linear transponder relays a whole slice of spectrum instead, often tens of kilohertz wide. Several SSB and CW contacts can share it at once, each in its own part of the passband. Finding your own signal there takes a map from uplink frequency to downlink frequency, and on many satellites that map runs backward.

10.6 APRS and Mesh Networks

Mon, 01 Jan 0001 00:00:00 +0000

Section 10.6: APRS and Mesh Networks #

A balloon’s position report may need a relay before your station can hear it. A mesh-network message may likewise need to cross several radio links. Both systems extend reach, but in different ways. The Automatic Packet Reporting System (APRS) limits repeats through each packet’s path, while a mesh finds its neighboring nodes and chooses routes between them.

Follow an APRS Report #

A high-altitude balloon carrying a small transmitter sends its changing position on its own schedule, without waiting for anyone to ask. Receiving stations plot each report on a map as it arrives.