Horizontal Dipole vs Inverted Vee Dipole

Discussion in 'General Technical Questions and Answers' started by W8EFA, Dec 16, 2004.

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1. W8EFAHam MemberQRZ Page

I know a regular dipole when hung flat top would have a figure 8 pattern basically broadside to the antenna (if dipole is run n-s lobes would radiate e-w).

If you take the same dipole and turn it into a Inverted Vee with the center up in the air and the ends toward the ground at a 45 degree angle will it still radiate broadside or will it be omni-directional like a vertical now?

2. W9GBHam MemberQRZ Page

Bill -

Think of the &quot;figure 8&quot; as 3-dimensional lobes.  When you go from a horizontal dipole to an inverted V ... your theoretical 72 ohm impedance at the feedpoint begins to drop and the lobes are no longer parallel to the horizon, but at a 45 degree angle to the horizon ... so it will have some characteristics of both ... and since the ends of these lobes are now closer to the ground .. this pattern will be influenced by the antenna's height, nearby ground objects, etc.

w9gb

3. KA5SSubscriberQRZ Page

Pretty much omnidirectional. Imagine a dipole pattern at an angle like the inverted V's wire added over the existing one; it fills in the nulls.

You don't have to be persnickety about pointing a dipole; they arent that directional, except for the nulls off the ends. A dipole can be oriented 45 or 60 degrees &quot;off&quot; and still work fine. An inverted V is even less fussy.

A lot of us can't put even a dipole up very high. Low dipoles direct most of their signal upwards, and are otherwise essentially nondirectional. For this kind of work -- Near Vertical Incidence Skywave, it's called -- both a low dipole and a low inverted V work about the same. The inverted V could beat a low dipole for non-NVIS work off the ends. Inverted V's have a lower angle of radiation (vertically polarized) as you get away from broadside, than a flat dipole.

Hope that helps.

Cortland
Ka5S

4. W5DXPHam MemberQRZ Page

The free demo version of EZNEC will answer questions like this one. It's available at: http://www.eznec.com
--73, Cecil, W5DXP

It depends on the frequency and how high the inverted vee is, proportional to operating wavelength.

If you build a 144 MHz (two meter) inverted vee and stick it up 30' above ground, it will have a figure-8 pattern like a horizontal dipole does. So will a non-inverted vee (that is, a dipole with a low center and higher ends). In fact, since 30' at 144 MHz is about five wavelengths, it pretty much won't matter if the vee is inverted or not, the antenna's effectively in free space anyway.

At HF, a lot changes because most of us can't get our antennas up high enough to have the pattern we think it should. Then, ground reflection is also very helpful, to the extent that it's not uncommon for a dipole to have several dB gain &quot;over a dipole,&quot; at some angles.

My 40-80-160m inverted vee (it's 80-meter sized, with 40m traps and 80m traps that act as loading on 160) has a very distinct &quot;dipole like&quot; pattern on 40 meters but becomes more omnidirectional, with a higher radiation angle than I'd usually like to have, on 80 and 160. It's up about 55 feet above ground.

WB2WIK/6

6. W4EETHam MemberQRZ Page

I have built a portable 20 meter inverted V that folds up toward the center. It is light weight and I can raise and lower it when I want to. I stripped out 3 Phelps Dodge fiberglass boat antennas which are my poles. The mast is made of aluminum conduit which extends to about 20 feet high (it looks like a telloscopping flag pole). The antenna plugs onto the top of the mast. This setup puts the center of the V about 32 feet high. My antenna is called a fat dipole. It has 2 elements on each side instead of one. This increases the overall size of the effective elements on each side. The radiated signal is low. I only get about 1 S unit difference when I rotate the antenna, so like these guys have said it is pretty much omni directional. It works great on DX and I have worked several European countries on 20 meters: Yugoslovia, Czech Republic, Norway, Scotland and others.