Grantville Gazette IX by Eric Flint

Author:Eric Flint [Flint, Eric]
Language: eng
Format: epub
Tags: Science fiction; American, Fantasy, Seventeenth century, Space Opera, Alternative histories (Fiction); American, General, Science Fiction, Adventure, Fantasy fiction; American, Fiction, Short Stories
Published: 2011-02-02T00:00:00+00:00

* * *

Two years before, the pages of books in the Ring of Fire had started flapping like butterfly wings. Now storms were brewing in far away Moscow. Economic storms, technical storms . . . to be followed,

perhaps, by political storms.

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Framed

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Contents

FACT:

Radio in 1632, Part 3

by Rick Boatright

In our two previous discussions of telecommunications in the 1632 series, we focused on radio

communications uniquely available to up-timers ("Radio in the 1632 Universe," Grantville Gazette,

Volume One) , and to wired communications ("So You Want to do Telecommunications in 1633,"

Grantville Gazette, Volume Two). In this article we will discuss radio options available to down-timers

both for transmitters and receivers. This will require a brief discussion of radio theory, which we will

restrict to no more than one equation.

As discussed in Grantville Gazette , Volume One, up-timers are generously supplied with radio

equipment. Various categories include CB radios, FRS handhelds, commercial FM radios for utility and

police work, ham radios in a variety of bands and "down-time built from up-time parts" radios including

the transmitter for the Voice of America. As well, there are custom military and diplomatic "cw" radios.

Down-timers want radios for a variety of reasons; people anywhere near Grantville want to listen to the

Voice of America radio station. Starting in early 1635, its sister station, the Voice of Luther in

Magdeburg will go on the air. People, especially governments and military types further from Grantville,

want the magic instantaneous communications over great distances that radio gives you.

How can they do either of those things without tubes, or transistors, or the other things we think of when

we say "electronics"?

The magic word is "detector."

Take a telephone receiver. In a telephone circuit. current flows through the handset and is stronger or

weaker according to the signal sent by the telephone transmitter. So the diaphragm in the receiver moves

in and out, attracted to the electromagnet more or less depending on there being more or less electricity

flowing through it.

If we have an antenna attached to a handset and then to ground, and we put the antenna near an AM

radio transmitter, the transmitter makes its radio signal stronger or weaker, just like the telephone current

is stronger or weaker in response to varying sounds. That radio energy is received by the antenna,

passed through the receiver, and into the ground. We ought to be able to hear it. But we hear nothing . . .

why? It's because the radio waves are going BACK AND FORTH, positive and negative, many, many

thousands of times per second. The oscillations are so fast that the diaphragm of the receiver just sits

there. Nothing happens.

We need a way to DETECT the RF currents. The first detectors used in commercial radios were called

"coherers." Edward Branly developed the first workable ones. Imagine a glass tube filled with sharply cut

nickel and silver shavings. Hook a battery and an earphone to the tube. The high resistance of the

shavings prevents electricity from flowing through the tube, and you hear nothing. But, if we also hook the

tube up to our antenna and ground, and there is a strong radio signal in

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