Harold,
The answer is no.
The radiation pattern simply changes depending on how much is bent and if the ends of a dipole are bent nearer ground or to the side where ground reflection is uniform. Fine tuning can be done by angle of bend.
From a figure in the QSL Bent Dipoles site for “Bent Down Ends”: The 4NEC2 modeling shows as the bend point is increased to 50% length, gain gradually goes down little more than a half dB. SWR goes down to a minimum at 60% and rises at 50%. Shorter than 50% the SWR rises quickly. The total length of wire necessary to maintain resonance gradually increases up to the 50% bend point then decreases past that.
The associated polar graph and 3D picture at the 50% bend point show a typical dipole shape only slightly fatter than a standard dipole. Two other 3D pictures show separately the major horizontal radiation and the smaller amount of vertical radiation from the bent ends.
Quoting “The modeling software makes it clear that you can bend the ends of a horizontal dipole with very little change in antenna performance, just some retuning is required”.
Looking at another figure: “Dipole, Laterally Bent-ends”, modeling shows that when bending to the same side, the decrease in gain is the same as a bent down dipole. The length of wire to maintain resonance will increase up to around 3% as the bend point approaches 50%. SWR shows a minimum at 60% bend rising rapidly past 50% bend.
Another figure about bending to opposite sides is noticeably different. In this form the gain drops only slightly until bends reach 50% to 30% but does not rise “off-the-map” like same-side antennas. SWR is lowest when the dipole is 60% long at the bends then rises 30 % and interestingly falls again because the long bends are radiating broadside which skews the RF pattern. The amount of wire needed increases steadily to over 4% longer as the bend points reduce the dipole to less than 40% length.
For fine tuning near 1:1 SWR, changing the angle of bend has the effect of changing the resonant length of the dipole. With right angle bends in the same direction: Rule
If the impedance is greater than 50 Ohms, increase the angle of bend.
If the impedance is less than 50 Ohms, reduce the angle of bend.
The greater the bend the longer you must make the wire to keep in tune...
2-3% longer for up to a 90 degree bend. Up to 10 to 15% longer when greater than a 90% bend. Roughly double the % increase for every 30 degrees of bend.
The above information comes from a web site about 4NEC2 modeling of the many ways to bend a dipole for space limited situations. Here is the link.
http://www.qsl.net/kk4obi/Center-fed%20Dipole%20selection.html
To see the “Bent Dipoles” discussions, figures and 3D pictures mentioned above, select Center-fed bent-end dipoles bent Horizontally or Laterally.
Consider also selecting Folded-end dipoles. And, if you sometimes like to think out-of-the-box, take a look at zig-zag and particularly multi-catenary techniques that are so set-up tolerant yet and perform so well.
Dick Reid