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Radio: Difference between revisions
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→Random wire antennae for hobby and amateur radio bands
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During emergencies hobby and amateur radio (HAM) bands can be a source of valuable information. Radio operators operating in their homes or 'radio shack' may send broadcasts on popular 20M, 40M and 80M bands. These are long-distance bands, sometimes covering hundreds or thousands of kilometers, and so this should be kept in context when seeking information. It is also important to beware the operators of these bands are not necessarily providing authoritative situational status information. For this reason, AM/MW bands should be the preferred choice for reception when mobile data and Internet connectivity is not possible. | During emergencies hobby and amateur radio (HAM) bands can be a source of valuable information. Radio operators operating in their homes or 'radio shack' may send broadcasts on popular 20M, 40M and 80M bands. These are long-distance bands, sometimes covering hundreds or thousands of kilometers, and so this should be kept in context when seeking information. It is also important to beware the operators of these bands are not necessarily providing authoritative situational status information. For this reason, AM/MW bands should be the preferred choice for reception when mobile data and Internet connectivity is not possible. | ||
If you are wanting to listen to broadcasts from popular amateur radio bands, which have far larger wavelengths (like 40M, 80M), you can try any very long wire you can get your hand on. Very long wires can allow for tuning across several bands, as the wire will include 1/4, 1/2 and perhaps even full wavelength representations. Using any long wire without a balun will often result in reception suffering from Standing Wave Ratio (SWR) interference due to differences in impedance between the antenna itself and the feedline to the receiver <ref>https://en.wikipedia.org/wiki/Standing_wave_ratio#Practical_implications_of_SWR</ref>. If you are without a balun, you can carefully select a wire for minimum interference. Physicists have studied random wire electromagnetic fields in relation to the SWR phenomenon, and with the aid of computer modeling have determined ideal lengths for minimal interference. J. C. Sprott, a physicist at University of Wisconsin, USA | If you are wanting to listen to broadcasts from popular amateur radio bands, which have far larger wavelengths (like 40M, 80M), you can try any very long wire you can get your hand on. Very long wires can allow for tuning across several bands, as the wire will include 1/4, 1/2 and perhaps even full wavelength representations. Using any long wire without a balun will often result in reception suffering from Standing Wave Ratio (SWR) interference due to differences in impedance between the antenna itself and the feedline to the receiver <ref>https://en.wikipedia.org/wiki/Standing_wave_ratio#Practical_implications_of_SWR</ref>. If you are without a balun, you can carefully select a wire for minimum interference. Physicists have studied random wire electromagnetic fields in relation to the SWR phenomenon, and with the aid of computer modeling have determined ideal lengths for minimal interference. An example is J. C. Sprott, a physicist at University of Wisconsin, USA<ref>https://sprott.physics.wisc.edu/technote/randwire.htm</ref>. | ||
==== Wavelength calculation ==== | ==== Wavelength calculation ==== | ||