Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
At low frequencies (such as AM broadcast), arrays of vertical towers are used to achieve directionality  and they will occupy large areas of land. For reception, a long Beverage antenna can have significant directivity. For non directional portable use, a short vertical antenna or small loop antenna works well, with the main design challenge being that of impedance matching. With a vertical antenna a loading coil at the base of the antenna may be employed to cancel the reactive component of impedance; small loop antennas are tuned with parallel capacitors for this purpose.
What is a problem one might encounter when using a portable antenna?
A: impedance matching

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From around 750, during the Abbasid Caliphate, women “became renowned for their brains as well as their beauty”. In particular, many well known women of the time were trained from childhood in music, dancing and poetry. Mahbuba was one of these. Another feminine figure to be remembered for her achievements was Tawaddud, "a slave girl who was said to have been bought at great cost by Hārūn al-Rashīd because she had passed her examinations by the most eminent scholars in astronomy, medicine, law, philosophy, music, history, Arabic grammar, literature, theology and chess". Moreover, among the most prominent feminine figures was Shuhda who was known as "the Scholar" or "the Pride of Women" during the 12th century in Baghdad. Despite the recognition of women's aptitudes during the Abbasid dynasty, all these came to an end in Iraq with the sack of Baghdad in 1258.
 Who was the least well known female scholar in Islamic schools?
A: unanswerable

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Motorcycles are also commonly used, particularly in locations that a car may not be able to reach, to control potential public order situations involving meetings of motorcyclists and often in escort duties where motorcycle police officers can quickly clear a path for escorted vehicles. Bicycle patrols are used in some areas because they allow for more open interaction with the public. In addition, their quieter operation can facilitate approaching suspects unawares and can help in pursuing them attempting to escape on foot.
How don't bicycles help catch some suspects?
A: unanswerable

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Since the system's launch, production costs have been reduced significantly as a result of phasing out the Emotion Engine chip and falling hardware costs. The cost of manufacturing Cell microprocessors has fallen dramatically as a result of moving to the 65 nm production process, and Blu-ray Disc diodes have become cheaper to manufacture. As of January 2008, each unit cost around $400 to manufacture; by August 2009, Sony had reduced costs by a total of 70%, meaning it only costs Sony around $240 per unit.
As of Summer 2008, what was the cost to Sony to make a PS3?
A:
unanswerable