The range of a heliograph depends on the opacity of the air and the effective collecting area of the mirrors. ![]() In some other circumstances, though, a narrow beam made it difficult to stay aligned with a moving target, as when communicating from shore to a moving ship, so the British issued a dispersing lens to broaden the heliograph beam from its natural diameter of 0.5 degrees to 15 degrees. In the Boer War, where both sides used heliographs, tubes were sometimes used to decrease the dispersion of the beam. However, anyone in the beam with the correct knowledge could intercept signals without being detected. It was very portable, did not require any power source, and was relatively secure since it was invisible to those not near the axis of operation, and the beam was very narrow, spreading only 50 feet per mile of range. It allowed long distance communication without a fixed infrastructure, though it could also be linked to make a fixed network extending for hundreds of miles, as in the fort-to-fort network used for the Geronimo campaign. This type produced flashes by a shutter mounted on a second tripod (Fig 4). Signal Corps heliograph mirror did not tilt. If the sun was behind the sender, the sighting rod was replaced by a second mirror, to capture the sunlight from the main mirror and reflect it to the receiving station. If the sun was in front of the sender, its rays were reflected directly from this mirror to the receiving station. The flashes were produced by a keying mechanism that tilted the mirror up a few degrees at the push of a lever at the back of the instrument. This indicated that the sunbeam was pointing at the target. ![]() They then turned up the sighting vane, which covered the cross wires with a diagram of a cross, and aligned the mirror with the tangent and elevation screws so the small shadow that was the reflection of the unsilvered spot hole was on the cross target. Keeping their head still, they then adjusted the aiming rod so its cross wires bisected the target. The sender aligned the heliograph to the target by looking at the reflected target in the mirror and moving their head until the target was hidden by the unsilvered spot. It used a mirror with a small unsilvered spot in the centre. Most heliographs were variants of the British Army Mance Mark V version (Fig.1). Fuess in Berlin (on display at the Museum of Communication in Frankfurt) Send us feedback about these examples.Fig. These examples are programmatically compiled from various online sources to illustrate current usage of the word 'helo.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. 2018 This helo can also carry fire retardant to slow down the fire’s spread. ![]() Joe Pappalardo, Popular Mechanics, 10 Sep. ![]() 2018 These units are not just aiming at Russian helos and warplanes anymore. Eric Adams, WIRED, 5 July 2019 These new helos will take on the mission to tackle these threats. 2020 The helicopter also shows off its quiet mode, deactivating the rear propeller and flying as a conventional helo. Alex Hollings, Popular Mechanics, 20 June 2021 Because of its additional, night-flying capability, the helo will likely need some bright lighting. 2021 So the Army looked for a helo that could fight back, a chopper that was purpose-built for an air assault role. Kyle Mizokami, Popular Mechanics, An aircrew on an MH-60 Jayhawk helo, hoisted and transported the hunting party, 6 adults and 1 teen, to awaiting EMS in Nome. Recent Examples on the Web As the attacker, Russia’s helicopters will be put in more vulnerable situations than Ukraine’s, as the helos are sent to areas where the enemy is expected to be dug in and waiting for them.
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