While I agree with Jim's information, I would point out the flat dipole
will have 3 dB more signal off of its broadside 0/180° as compared to
that of a inverted V dipole off of its broadside. At the same time, the
inverted V dipole will have about 4.5 db more signal off of its ends
90/270° as compared to that of a flat dipole off of its ends.
It appears what one loses with one antenna is made up with the other
antenna depending on azimuth and apex angle of the inverted V being
somewhat greater than 90°. In fact it appears that the Inverted V has
almost an omnidirectional pattern at an elevation angle of 25°. Fig 9.6
If a close match to 50 ohms is required, it is best to adjust the angle
for lowest SWR while maintaining resonance by adjustment of the length.
Reference: ARRL Antenna Book, 22nd Edition, 9.1.3 Inverted-V Dipole
73
Bob, K4TAX
On 12/7/2018 6:51 PM, Jim Brown wrote:
On 12/7/2018 12:55 PM, Dick Dickinson wrote:
Why is there so much promotion of dipole antennas over inverted vee
type antennas?
As has been noted, an inverted vee is a compromise dipole -- the sort
of thing you can rig with a single support. A flat dipole with its
center at the same height as the inv vee will have a dB or two more
gain, and the directional pattern will be the classic "figure-eight"
pattern with broad peaks broadside to the wire and nulls off the ends.
Inverted vees tend to lose the nulls off their ends. All this stuff is
in the ARRL Handbook and Antenna Book which every ham should own and
study as we have time.
For rigging heights that are possible for most hams, horizontal
antennas for 160 or 80, and 40M over flat terrain produce more gain at
greater height. It is a fallacy that an antenna must be low to work
short distances. Low antennas radiate LESS signal at high angles than
high ones. I published a study of this several years ago. It's here.
http://k9yc.com/AntennaPlanning.pdf beginning on page 10. Field
strength at 70 degrees vertical elevation just starts to fall off as
it is raised to 1/3 wavelength. That's 45 ft on 40M, 90 ft on 80M, 180
ft on 160M.
73, Jim K9YC
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