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This article is from the Shortwave radio FAQ, by Ralph Brandi rbrandi@lucent.com with numerous contributions by others.

07 Could you explain the frequencies used? What's the 49 meter band? etc. (Shortwave radio)

As you tune around, you'll notice certain kinds of signals tend to be
concentrated together. Different services are allocated different frequency
ranges. International broadcasters, for instance, are assigned to ten
frequency bands up and down the dial. These are:

3900-4000 kHz (75 meter band)         13600-13800 kHz (22 meter band)
5950-6200 kHz (49 meter band)         15100-15600 kHz (19 meter band)
7100-7300 kHz (41 meter band)         17550-17900 kHz (16 meter band)
9500-9900 kHz (31 meter band)         21450-21850 kHz (13 meter band)
11650-12050 kHz (25 meter band)       25600-26100 kHz (11 meter band)

In general, lower frequencies (below 9000 kHz) are better received at night
and for a few hours surrounding dawn and dusk, and higher frequencies (13000
kHz and up) are better received during the day. The frequencies in between
are transitional, with reception being possible at most times. In practice,
these guidelines are not absolute, with reception on high frequencies being
possible at night, and lower frequencies can provide decent medium-distance
reception during the day. Additionally, these numbers can change slightly
with the changing of the sunspot cycle, which affects the ionization of the
upper atmosphere, and hence the propagation of shortwave signals. In times of
lower sunspot activity, as is the case in 1995-96, higher frequencies are
generally less useful than lower frequencies, and the range of frequencies
used at any given time of day is generally shifted slightly downward.

Hams (who have their own newsgroups, rec.radio.amateur.*) and point-to-point,
or utility communications, fill most of the rest of the frequencies. The
Confidential Frequency List and The Shortwave Guide mentioned above can
provide more information on what can be heard in these areas, as can utility
loggings in magazines like Monitoring Times and Popular Communications, and in
club bulletins.

 

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