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Doing it with milliwatts

  At least some amateurs are competitive and like to measure their achievements against others. In the early days of HF radio it was all about distance. Then, as worldwide contacts became more common (at least on bands like 20 metres) from the 1930s it became DX countries worked. Though long distances continued to be sought for the more challenging DX bands such as 1.8 and 3.5 MHz along with VHF, UHF and higher.

QRPers came up with another way of comparing their achievements. Instead of a straight distance worked they divided it by power. Called 'Miles per Watt' it sought to compensate for lower power. A still-available award called '1000 miles per watt' was launched. You'd qualify if you worked 10000 miles with 10 watts, 1000 miles with 1 watt or 100 miles with 100mW. This is not very scientific; double the power does not double the distance and half the power does not halve the distance. Consequently the easiest way to reach 1000 miles per watt is not to seek increased distance as much as to seek to cover a given distance with progressively lower output powers.

Which brings us to milliwatts. Single hop HF, sporadic-E lower VHF and enhanced tropospheric VHF/UHF propagation are all low-loss propagation modes. Milliwatts can readily carry several hundred to a couple of thousand kilometres via these means. This is even with common transmitting modes such as CW and SSB. The following are some video examples.

Milliwatts from a hand-powered CW transmitter (500mW)

Milliwatts HF SSB

Milliwatt contesting (down to 20mW)

Homebrew milliwatt DSB beacon (40mW)

Milliwatts with slow scan TV (down to 20mW)

Milliwatts WSPR

A spontaneous 144 MHz opening (down to 500mW)



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