23 Jan 19

Also called a “beam antenna”, or “parasitic array”, the Yagi is very widely used as a high-gain antenna on the HF, VHF and UHF bands. It has moderate to high gain which depends on the number of elements used, typically limited to about 20 dBi, linear polarization,  unidirectional (end-fire) beam pattern with high front-to-back ratio of up to 20 db. and is lightweight, inexpensive and simple to construct. The bandwidth of a Yagi antenna, the frequency range over which it has high gain, is narrow, a few percent of the center frequency, and decreases with increasing gain,  so it is often used in fixed-frequency applications. The largest and best-known use is as rooftop terrestrial television antennas, but it is also used for point-to-point fixed communication links, in radar antennas,[ and for long distance shortwave communication by shortwave broadcasting stations and radio armatures.

Source… Wikipedia

22 Jan 19

The Rhombic Antenna is an equilateral parallelogram shaped antenna. Generally, it has two opposite acute angles. The tilt angle, θ is approximately equal to 90° minus the angle of major lobe. Rhombic antenna works under the principle of travelling wave radiator. It is arranged in the form of a rhombus or diamond shape and suspended horizontally above the surface of the earth.

Source: Antenna Theory

Rhombic Antenna… Wikipedia

18 Jan 19

Chew the fat dates back to the first time in print and that is 1885, from a book written by J Brunlees Patterson called “Life in the Ranks of the British Army in India”.  In his book chew the fat was referencing army soldiers gossiping amongst themselves and the junior officers to keep from being bored. This may not be its beginning but it is for its use associated with conversation, the term does go back to when a fat soaked rag end was bitten off to be wrapped around a musket ball while loading. 

More at Wikipedia

17 Jan 19

Chew the rag, although its original origin is unknown was first in print in the 1875 printing of “The Random House Historical Printing of American Slang”, and then in 1885 appeared in the same sentence in a book “Life in the Ranks of the British Army in India”.

Some speculate that the term relates too cloth and ladies sewing circles or women gossiping while quilting.

Source: Wikipedia

13 Jan 19

Paul Horowitz

At age 8, Horowitz achieved distinction as the world’s youngest amateur radio operator. He went on to study physics at Harvard University (B.A., 1965; M.A., 1967; Ph.D., 1970), where he has also spent all of his subsequent career. His early work was on scanning microscopy (using both protons and X-rays). Horowitz has also conducted astrophysical research on pulsars and investigations in biophysics. His interest in practical electronics has led to a handful of inventions, including an automated voting machine and an acoustic mechanism for landmine detection. Since 1974 he has taught a practical course in electronics whose lecture notes became one of the best known textbooks in the field: The Art of Electronics (coauthored with Winfield Hill).

Source, Wikipedia


10 Jan 19

At night, solar radiation ceases and the free electrons recombine with their host molecules. The D-layer completely disappears and offers no signal loss. The E/F layers merge into a single layer, but remain reflective to HF signals.

However, this combined layer has a lower electron density than daytime levels, lowering the MUF. Astronomers call these ionization layers plasma layers and the lowest frequency that escapes into space the plasma frequency, fp. QRPers look at it just opposite – what is the highest frequency that does not escape into space?

We call this the maximum usable frequency or MUF. In reality, the MUF and plasma frequency are exactly the same.