Wikipedia:Reference desk/Archives/Science/2018 November 1
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November 1
[edit]Why was the Warsaw Radio Mast a half wave tall instead of quarter wave?
[edit]What benefit did half wave have that quarter wave didn't? Sagittarian Milky Way (talk) 20:01, 1 November 2018 (UTC)
- You should read Dipole_antenna#Dipole_variations. Ruslik_Zero 20:09, 1 November 2018 (UTC)
- Why wasn't it a quarter wave monopole? Sagittarian Milky Way (talk) 20:15, 1 November 2018 (UTC)
- The feed impedance will be very different. For a quater wave monopole this might be around 37.5 Ohms, but the end of the halfwave monopole has a high impedance. For the 2 MW / 120kV combo this is about 7200 Ohms, which probably fits in much better with the valves in the transmitter used to drive the antenna, and avoids the use of a large transformer making a high current. However I would expect that a the cost of a huge transformer may have been less than building the world's highest structure. Secondly the radiation pattern is doubled along the horizontal, so that the power is effectively doubled. Graeme Bartlett (talk) 08:55, 2 November 2018 (UTC)
- Why wasn't it a quarter wave monopole? Sagittarian Milky Way (talk) 20:15, 1 November 2018 (UTC)