The 40 metre amateur radio band is one of the most popular and useful bands available to radio amateurs. It’s been a favourite of operators for generations because of its ability to provide both relatively short-distance communications and worldwide contacts.
Unlike the higher HF bands, which can become almost unusable during periods of low solar activity, 40 metres is remarkably dependable. It is particularly good for communication throughout Britain and Europe during daylight hours, while at night it frequently opens up to stations thousands of miles away.
Frequencies and band allocation
In the UK, the 40 metre band extends from 7.000 MHz to 7.200 MHz, giving radio amateurs 200 kHz of spectrum.
The UK follows the IARU Region 1 band plan, which divides the band into sections for different operating activities.
Propagation characteristics
One of the most interesting features of 40 metres is how its propagation changes throughout the day.
During daylight
The band is particularly useful for contacts across Britain and neighbouring European countries. Radio signals are refracted back towards Earth by the ionosphere, often making contacts over several hundred miles possible with modest equipment.
During the evening
As the Sun sets, absorption in the ionospheric D layer decreases. More distant European stations become stronger, and signals from North America and other continents may begin to appear.
During the night
The band often becomes an excellent medium for long-distance DX communication. Contacts with North America, Africa, Asia and occasionally Australia or New Zealand are possible when propagation conditions are favourable.
Why 40 metres works so well
Radio waves at 7 MHz are refracted by the ionosphere, principally its F region, allowing signals to travel far beyond the horizon. During daytime, D-layer absorption reduces the strength of distant signals. At night, this absorption largely disappears, permitting signals to travel over much greater distances.
The band also supports Near Vertical Incidence Skywave (NVIS) propagation. With a suitable horizontal antenna, signals radiated at high angles can return to Earth relatively close to the transmitter, often providing useful communication over distances of approximately 50–500 km when ionospheric conditions permit. This makes 40 metres especially valuable for UK amateur radio nets and regional communications.
Aerials for 40 metres:
I use a 100 foot doublet antenna on 40 metres with my Icom IC-7300. The antenna is great on 80 60 and 40 metres but results are not so good on the higher frequency bands. I use vertical aerials for those bands. I also have a 160 foot end-fed wire up at about 20 feet. This works extremely well on 40 metres with my Clansman RT-320.
This is my favourite band for the time being as it suffers the least noise and interference. Sadly, 80 and 160 metres are wiped out with noise. Even the 5MHz frequencies are plagued with noise at my QTH.
The 160 foot end-fed loads beautifully with the internal ATU in my Clansman PRC-320. Obviously the antenna is far too long for this band, but it works incredibly well. Bearing in mind that the PRC-320 only puts out 30 Watts, the punchy and toppy audio smashes through pileups.
More coming soon...