The most significant factors here are that the elements are fed 180 degrees out of phase and are spaced 1/2-wavelength apart. In a half-wavelength a radio frequency signal differs by 180 degrees from the source. So, you can also say that the elements are spaced 180 degrees apart. Therefore, when a signal leaving one element reaches the other it is in phase with the radiation from the element it is reaching and thus the output of each element re-enforces the output from the other.

That means the pattern is essentially two overlapping circular outputs from the two elements and strengthened in the direction away from the antenna in each direction in line with the axis through the two antenna elements. In other words: a figure-8 oriented along the axis of the array.

See also: http://www.bellscb.com/cb_radio_hobby/antennas/antarray.html, last Fig

Memory tips from other users:

• "180 degrees" has an 8, so it's a figure eight answer. The signal is "O"ut of phase, so the pattern is "O"riented along the axis. Choose the answer with 180 and an "O" word. (See other easily confused similar question, E9C03, whose answer is a broadside figure 8.)

• Visualize a signal leaving one of the verticals as "slow" when heading off in any direction except through the other phased vertical, but when it leaves the first vertical element and travels "through" the area immediately surrounding the second vertical on its way to its intended target, it gets a little "boost" and speeds up. The "boost" effect is 'along the axis of the array' which, in other words, means when the two antennas are aligned, one in front of the other, on a path toward the intended target.

• "Half, Opposite, Along" - For 1/2-wavelength apart and 180 degrees out of phase (opposite), think of the figure-8 pattern stretching along the line connecting the two antennas. The word "Half" also visually resembles the figure-8 lying along the axis.

• "Out of Phase" and "Oriented" both start with the letter "O". Two O's make an 8. So look for "8" and "Oriented"

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See Figure 3 at: http://www.bellscb.com/cb_radio_hobby/antennas/antarray.html

Memory Tip: The "9" in 90 degrees looks a bit like a drawing of a cardioid shape.

Mnemonic: "Quarter, Quarter, Heart" - For 1/4-wavelength apart and 90 degrees out of phase, think of a cardioid, which resembles a heart shape. "Quarter, Quarter" for both the spacing and the phase creates an easy-to-remember connection to the cardioid shape.

Silly hack: Think of an index card (for cardoid). The angle of the card is 90 degrees at all corners.

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There are many ways to put up antennas that are directional. One way to get directionality without a tower is to use phased vertical arrays.

In general, the phased vertical array consists of two or more quarter-wave vertical antennas. The radiation pattern that the array will have depends on how you feed the vertical antennas.

So, for example, the radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed 180 degrees out of phase is a figure-8 oriented along the axis of the array. (E9C01) The radiation pattern of two 1/4-wavelength vertical antennas spaced 1/4-wavelength apart and fed 90 degrees out of phase is a cardioid. (E9C02) The radiation pattern of two 1/4-wavelength vertical antennas spaced 1/2-wavelength apart and fed in phase is a Figure-8 broadside to the axis of the array. (E9C03)

Source kb6nu.com - Extra Class question of the day: Wire and phased vertical antennas

Memory Tips from other users:

• "In phase" is pretty standard, and a dipole is pretty standard. So the pattern is roughly the same as a dipole: a figure-8 broadside to the antenna.

• "Half, Same, Broadside" - For 1/2-wavelength apart and in phase (same phase), visualize the figure-8 broadside to the axis. The word "Broadside" helps to remember that the pattern is oriented perpendicular to the line connecting the two antennas.

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The rhombic antenna is diamond shaped, each side at least one wavelength long, and is good because of simplicity and it's ability to operate over a wide range of frequencies. Takes a Lot of space, though.

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They require a huge field and space and supports if you are thinking of putting one of these in your backyard you better have a huge property. Of course there are some that are not spaced that much. Look at the picture. https://www.google.com/search?q=rhombic+antenna&safe=active&um=1&ie=UTF-8&hl=en&tbm=isch&source=og&sa=N&tab=wi&ei=gWPOUKzECcLCyQGx-oCwAQ&biw=1680&bih=949&sei=j2POUNuRCcqSyQH284GoCA

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Normally, a rhombic antenna is bi-directional along the longer axis; adding a terminating resistor, usually in the 600 ohm range, at the vertex opposite to the feedpoint makes the rhombic unidirectional in the direction from feedpoint to resistor.

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The main effect of placing a vertical antenna over an imperfect ground is that it reduces low-angle radiation. Mounting it over seawater (a very even and highly conductive surface) will increase the low-angle radiation.

Both this question and E3A07 involve signal propagation and terrain features. While the physics involved in the questions are different, the correct answer to both questions is the one where your signal goes farther across water. (Discounting bounces, low angle emissions go "farther" over water, because most of the energy is directed horizontally.)

Silly Hint: If you increase the radiation enough, you might create a sea monster!

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According to Wikipedia: "A Beverage consists of a horizontal wire one or two wavelengths long (hundreds of feet at HF to several kilometres for longwave) suspended above the ground, with the feedline to the receiver attached to one end and the other terminated through a resistor to ground."

http://en.wikipedia.org/wiki/Beverage_antenna

Memory Hint: Beverage antennas are receive antennas. When receiving a beverage, you want a receiver (glass) that's at least big enough to hold the the pour (beverage). When receiving RF, you want an antenna at least big enough to hold a wave.

Hint: long question - 'long' in answer

Hint 2: my favorite Beverage is a long drink.

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