The only amateur medium-frequency band is situated

just above the domestic AM broadcast band. Ground

wave provides reliable communication out to 150 km

(90 mi) or during the day, when no other form of

propagation is available. Long-distance paths are made

High Frequencies (3-30 MHz)

A wide variety of propagation modes are useful on the

HF bands. The lowest two bands in this range share

many daytime characteristics with 160 m. The transition

between bands primarily useful at night or during the

day appears around 10 MHz. Most long-distance

more exotic propagation, including TE, sporadic E,

aurora and meteor scatter, begin to be practical.

3.5-4.0 MHz (80 m)

The lowest HF band is similar to 160 m in many

respects. Daytime absorption is significant, but not

quite as extreme as at 1.8 MHz. High-angle signals

may penetrate to the E and F layers. Daytime communication

range is typically limited to 400 km (250 mi) by

ground-wave and skywave propagation. At night,

signals are often propagated halfway around the

world. As at 1.8 MHz, atmospheric noise is a nuisance,

making winter the most attractive season for the

80-m DXer.

5.3-5.4 MHz (60 m)

This newest HF band allows USB operation at a

50 W PEP ERP level on five channels between roughly

5.3 and 5.4 MHz. The distance covered during daytime

propagation will fall in between that achievable on the

80 m and 40 m bands — about 600 km with a typical

station. At night, worldwide propagation is possible in

spite of the relatively low power limit. Signal strengths

will typically be higher than on 80 m but not as high as

on 40 m.

7.0-7.3 MHz (40 m)

The popular 40-m band has a clearly defined skip

zone during the day. D-layer absorption is not as

severe as on the lower bands, so short-distance skip

via the E and F layers is possible. During the day, a

typical station can cover a radius of approximately

800 km (500 mi). Ground-wave propagation is not

important. At night, reliable worldwide communication

a 24-hour basis, but during a solar minimum, the MUF

on some DX paths may drop below 10 MHz at night.

Under these conditions, 30 m adopts the characteristics

of the daytime bands at 14 MHz and higher. The

30-m band shows the least variation in conditions over

the 11-year solar cycle, thus making it generally useful

for long-distance communication anytime.

14.0-14.35 MHz (20 m)

The 20-m band is traditionally regarded as the

amateurs’ primary long-haul DX favorite. Regardless

of the 11-year solar cycle, 20 m can be depended on

during the day. During solar-maximum periods, 20 m

will often stay open to distant locations throughout the

night. Skip distance is usually appreciable and is

always present to some degree. Daytime E-layer

propagation may be detected along very short paths.

Atmospheric noise is not a serious consideration, even

in the summer. Because of its popularity, 20 m tends

to be very congested during the daylight hours.

18.068-18.168 MHz (17 m)

The 17-m band is similar to the 20-m band in many

respects, but the effects of fluctuating solar activity on

years of high solar activity, 17 m is reliable for daytime

and early-evening long-range communication, often

lasting well after sunset. During moderate years, the

band may open only during sunlight hours and close

shortly after sunset. At solar minimum, 17 m will open

to middle and equatorial latitudes, but only for short

periods during midday on north-south paths.

21.0-21.45 MHz (15 m)

The 15-m band has long been considered a prime

DX band during solar cycle maxima, but it is sensitive

to changing solar activity. During peak years, 15 m is

open well into the night. During periods of moderate

solar activity, 15 m is basically a daytime-only band,

closing shortly after sunset. During solar minimum

periods, 15 m may not open at all except for infrequent

north-south transequatorial circuits. Sporadic E

is observed occasionally in early summer and midwinter,

although this is not common and the effects

are not as pronounced as on the higher frequencies.

efficient that very low power can produce loud signals

halfway around the globe. DX is abundant with modest

equipment. Under these conditions, the band is usually

open from sunrise to a few hours past sunset. During

periods of moderate solar activity, 10 m usually opens

only to low and transequatorial latitudes around noon.

at any time during the day or night.

Sporadic E is fairly common on 10 m, especially May

through August, although it may appear at any time. Short

skip, as sporadic E is sometimes called on the HF bands,

has little relation to the solar cycle and occurs regardless

of F-layer conditions. It provides single-hop communication

from 300 to 2300 km (190 to 1400 mi) and multiplehop

opportunities of 4500 km (2800 mi) and farther.

Ten meters is a transitional band in that it also shares

some of the propagation modes more characteristic of

VHF. Meteor scatter, aurora, auroral E and transequatorial

spread-F provide the means of making contacts out

to 2300 km (1400 mi) and farther, but these modes often

go unnoticed at 28 MHz. Techniques similar to those

used at VHF can be very effective on 10 m, as signals are

usually stronger and more persistent. These exotic

modes can be more fully exploited, especially during the

solar minimum when F2 DXing has waned.

A wide variety of propagation modes are useful in the

VHF range. F-layer skip appears on 50 MHz during

solar cycle peaks. Sporadic E and several other E-layer

phenomena are most effective in the VHF range. Still

other forms of VHF ionospheric propagation, such as

field-aligned irregularities (FAI) and transequatorial

spread F (TE), are rarely observed at HF. Tropospheric

propagation, which is not a factor at HF, becomes

increasingly important above 50 MHz.

50-54 MHz (6 m)

The lowest amateur VHF band shares many of the

characteristics of both lower and higher frequencies. In

the absence of any favorable ionospheric propagation

conditions, well-equipped 50-MHz stations work regularly

over a radius of 300 km (190 mi) via tropospheric

scatter, depending on terrain, power, receiver capabilities

and antenna. Weak-signal troposcatter allows the

best stations to make 500-km (310-mi) contacts nearly

additional propagation mode for contacts as far as

4000 km (2500 mi) when the MUF is just below 50

MHz. TE paths as long as 8000 km (5000 mi) across

the magnetic equator are common around the spring

and fall equinoxes of peak solar cycle years.

Sporadic E is probably the most common and

certainly the most popular form of propagation on the

6-m band. Single-hop E-skip openings may last many

hours for contacts from 600 to 2300-km (370 to

1400 mi), primarily during the spring and early summer.

several times a year, and contacts between the US and

South America, Europe and Japan via multiple-hop

E-skip occur nearly every summer.

Other types of E-layer ionospheric propagation make

6 m an exciting band. Maximum distances of about

2300 km (1400 mi) are typical for all types of E-layer

modes. Propagation via FAI often provides additional

hours of contacts immediately following sporadic E

events. Auroral propagation often makes its appearance

in late afternoon when the geomagnetic field is

disturbed. Closely related auroral-E propagation may

extend the 6-m range to 4000 km (2500 mi) and

sometimes farther across the northern states and

Canada, usually after midnight. Meteor scatter provides

brief contacts during the early morning hours,

especially during one of the dozen or so prominent

annual meteor showers.

144-148 MHz (2 m)

Ionospheric effects are significantly reduced at

144 MHz, but they are far from absent. F-layer propagation

is unknown except for TE, which is responsible

for the current 144-MHz terrestrial DX record of nearly

8000 km (5000 mi). Sporadic E occurs as high as

144 MHz less than a tenth as often as at 50 MHz, but

the usual maximum single-hop distance is the same,

about 2300 km (1400 mi). Multiple-hop sporadic-E

contacts greater than 3000 km (1900 mi) have occurred

from time to time across the continental US, as

well as across Southern Europe.

Auroral propagation is quite similar to that found at

50 MHz, except that signals are weaker and more

Doppler-distorted. Auroral-E contacts are rare. Meteorscatter

contacts are limited primarily to the periods of

the great annual meteor showers and require much

patience and operating skill. Contacts have been made

via FAI on 144 MHz, but its potential has not been fully

explored.

Tropospheric effects improve with increasing

frequency, and 144 MHz is the lowest VHF band at

which weather plays an important propagation role.

Weather-induced enhancements may extend the

normal 300- to 600-km (190- to 370-mi) range of wellequipped

stations to 800 km (500 mi) and more,

especially during the summer and early fall. Tropospheric

ducting extends this range to 2000 km

(1200 mi) and farther over the continent and at least to

4000 km (2500 mi) over some well-known all-water

paths, such as that between California and Hawaii.