Photoshopping my models
80m dipole on 20 meters – rotated appropriately. Click for larger.
No, it’s not what you think…
I’ve recently been manipulating a modeled version on my 80m dipole to see what type of radiation pattern it produces on other bands. Since it’s fed with 450-ohm ladder line, it is useful on all bands 10-80 meters and for several years it was my only antenna.
Its radiation pattern on 40 and 80 meters is the predictable figure 8 – but on higher bands, things get more complex with numerous lobes and nulls so I thought it might be useful to see how these characteristics were oriented in relation to the dipole’s physical orientation.
My dipole is 75ft/23m high and is oriented along an axis of 333-153 degrees. In other words, it’s 27 degrees counterclockwise from true North-South.
DX Atlas allows anyone to make an azimuthal map centered on their location. EZNEC displays a pattern of an antenna’s radiation with North at the top (or at the 3 o’clock position). Therefore, it’s a simple matter of using image editing software to rotate the EZNEC image to correspond to the real-world antenna’s orientation.
With everyone being a “photographer” in this digital age (even me) many people have software that will accomplish this. I use Photoshop but many other programs will do just as well for this.
After a counter-clockwise rotation of 27 degrees (shown below), I placed the EZNEC image onto the DX Atlas image.
Manipulating the “scale” function allowed me to make each image the same size. The last step was a reduction in opacity (to 30%) of the top layer to allow the image underneath to be seen as well.
Anyone with a fixed-position antenna can use this way of seeing to which part of the world their antenna is likely to exhibit a strength or weakness.
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Themocracy
Hi John, really a nice way of photoshopping in our radio hobby. Though the pattern is of course is pure theoretical. In fact surroundings like your house, trees, your antennemast etc. will have a effect on it. I don’t have any clue what the pattern for my loop is besides 80m. I can’t tell if it is weak or strong in any direction. So I pressume it radiates to everywere…73, Bas
You’re right, Bas – electrical utility wiring, trees and other antennas all distort the actual pattern. I’m comparing this diagram with on-the-air results from my logbook and comparing the dipole to the Yagi. On some bands/directions, the dipole is equal to the Yagi – I made a similar plot to this one in an effort to see why that might be the case and in what other directions I might expect similar results.