|[AMRadio] Inverted V antenna|
k4kyv at charter.net
Mon Jan 25 13:15:34 EST 2016
The “cone of silence” of the null off the ends of a horizontal half-wave dipole is very narrow (or maybe “skinny” would be a better word), meaning it is limited to a very small range of vertical take-off angles, as well as horizontal coverage. For all practical purposes, a dipole, whether truly horizontal or inverted-vee, can be considered omni-directional, particularly on the 160m, 80m and 40m bands. The broadside advantage and end nulls are something blown way out of proportion in amateur radio lore, just like SWR.
“One frequently sees a dipole azimuth pattern depicting a very sharp null off of the ends of a dipole. While technically accurate, this can be very misleading ... and is a result of trying to depict a 3 dimensional pattern in 2 dimensions. **This often seen null is only evident at the same launch angle as the maximum broadside gain**. Of major significance is the large amount of gain off the ends at higher launch angles. Due to multiple lobes forming above ½ wavelength, this is not easily shown in tabular form.”
From: Jim Isbell, W5JAI [mailto:jim.isbell at gmail.com]
But the inverted "V" does have radiation off the ends because there is a vertical component. I have seen the charts, its not great but it is something. BUT the dipole is NUL off the ends. Yes, I will sacrifice gain off the sides to get some gain off the ends by going with the "V" but without a rotateable dipole it at least gives me some coverage I cant get any other way. I have only one way the antenna can be oriented. NE to SW which, from South Texas, puts Washington/Oregon and the Caribbean in the NULs.
>> If you turn it over, will a "V" antenna work the same if it isnt
> Doesn't that make it an inverted-inverted V? Isn't that the same as just a
I think you are confusing it with a horizontal vee or vee-beam. Besides, if
you have two tall supports to hold up the ends, why not go ahead and pull
the wire tight enough to raise the mid-point and make it a true horizontal
dipole? The inverted-vee is a compromise antenna designed to approach the
performance of a horizontal half-wave dipole using only one high support.
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