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April Fact-of-the-Day Index

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DateFact of the Day Topic
April 1Null Hypothesis In hypothesis testing, a null hypothesis is the hypothesis that is being tested. For example ...
April 2Speech Frequency Components Human speech frequency components change rapidly with time. They also tend to have ...
April 3Sound-Induced Hearing Loss Radio amateurs and others who listen to high-amplitude signals and noise for long time periods risk ...
April 4Human Differential Sound Intensity Sensitivity How much does the RF output of a CW or SSB transmitter have to be increased for a loudness change ...
April 5Compression and Expansion Only the peaks of an RF envelope can be heard when the peak-to-peak amplitude of an SSB signal is ...
April 6Dimension of a Space The number of coordinates needed to specify a point in a space is the dimension of the space. For example ...
April 7Geographic vs. Magnetic Poles The magnetic pole that is near earth's geographic north-pole is, of course, a south-pole, because ...
April 8Earth Magnetic Field Decline The earth's geomagnetic magnetic field strength was first measured in the 1830's. Since that time ...
April 9Earth Magnetic Field Distribution Earth's geomagnetic field is rather weak at and above the surface of the earth, but ...
April 10Earth Magnetic Reversal Frequency Studies of magnetization orientations in magnetic minerals in the earth have revealed ...
April 11Earth Magnetic Reversal Speed Some self-proclaimed experts have written books and magazine articles, and have been on radio talk shows ...
April 12Never Used Linux? Many computer users say they have never used Linux when in fact they use it almost every day ...
April 13Laser History Most people involved with electronics know the word laser is an acronym for Light Amplification by ...
April 14Multiple Coax Cable Feedlines Most modern communications radios have 50-ohm unbalanced antenna connections, but ...
April 1550 Hz vs. 60 Hz Power Transformers More iron and/or more turns of wire are required to have the same transformer winding ...
April 16UPS RFI That high noise level you have been blaming on the power company may be coming from under your desk ...
April 17Two Types of Ferrite There are two basic types of ferrite, hard ferrite and soft ferrite. However, those designations can be misleading, because ...
April 18Cleanup Windows Clutter Windows clutters computer hard disks with many unnecessary files. For example, detailed ...
April 19Ferrite Inductor DC Direct current can have large effects on the inductance of chokes, filters and transformers wound on ferrite cores ...
April 20Horizontal Antennas near Earth The feed-impedance of a horizontal antenna cycles above and below its free-space value as ...
April 21Kennelly-Heaviside Layer (Ionosphere) The existence of the ionosphere was independently surmised by Arthur E. Kennelly in ...
April 22Smith Chart A Smith Chart, also known as a Smith Diagram, is special type of chart that was developed to enable easy graphic solution of ...
April 23A Long Balanced Feedline is a Balun A current balun will make the radiation pattern of most center-fed dipole antennas more symmetrical ...
April 24Multiple Dipole Multiband Antennas Several halfwave dipoles that are resonant at different frequencies can be center-fed from a common ...
April 25Air Breakdown Voltage Air is a good insulator at low values of electric field strength, because electrons attach to atoms of oxygen faster...
April 26Large Horizontal Loop Antennas Large horizontal loops are popular HF antennas for good reasons. They tend to have generally similar ...
April 27New Lightning Theories Lighting has been generally considered in the past to be an extremely large electric spark. However, one of its most puzzling ...
April 28RF Balun Construction Both 1:1 and impedance transforming RF baluns of various designs are relatively easy to construct by ...
April 29Non-Contaminating Vinyl (NCV) Chemical plasticizers in coax cable jacket material, such as PVC, can leach or migrate through coax cable shields ...
April 30Underground Power Cable Faults Underground power distribution is now common in most upscale communities. There are many advantages ...

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