Wow, 200+ views in just 4 days!
Good for just 3 messages and nothing practical (still).
Well, just to make a brief resume or the article. Esentially it's just a series of concentrical circunferences (we are talking here
about a Prime Focus "dish", in an offset dish, instead of circunferences these would be ellipses, this is, a series of "concentrical"
ellipses, however that is not mentionated in the article), and finally it also recommends us to paint the antenna with metallic paint.
I don't want to explain here how this is supposed to work (in fact, I'm not sure If I have understood it
).
It's just something about the different interferences of the waves, so, it's supposed that the waves act finally like in a parabolic
dish. Also, it's interesting to note that the gain of the antenna does not depend at all of the diameter but of the number of zones (the number of "circunferences", to explain it easily). However this in fact a limitation, because increasing the number of zones for the same diameter, means that the radius between one and another circunference it's smaller than with less zones, and, in consecuence, it's more difficult to draw (and cut) the circunferences, especially if you want to do it without special/professional tool. So in fact, this is a good idea, but it will be probably a better idea with big diameters.
So I think we'll start here. The article includes a BASIC program (1985, remember
) that calculates the circunferences to cut if we
enter some information:
1.-The wanted number of zones.
2.-The wanted outside radius.
Well, no more speak, here is
the .bas code of the original program: http://usuarios.lycos.es/telefrancisco/plyweb/plywoodo.bas (The "o" stands for "Original"
) The file is just for reference. It's interesting as it does haves the formulas, but, however, I had some problems with it as it didn't showed up the correct results, so I have made:
a modification of the original file: http://usuarios.lycos.es/telefrancisco/plyweb/plywoodm.bas
(The "m" stands for "Modified")
As you can see it's not only a modification, because I have added also the calculation of the Theorical Gain of the designed antenna. If do you want to compile/modify it please note also that my BASIC compile calculates the natural logarithm (base "e" log, in LOG function, line 62) instead of the base 10 log. Appart from that add in lines 62 and 65, I have also modified the calculation of the square root (lines 70, 72 and 75), because as I said earlier the original program didn't calculate the correct result for me.
Also, there is a cosmetic change in Line 80.
Also, please note that, instead of the original it asks for the DIAMETER instead of the Radius (Line 55), as I think this will be easier as most of us currently think about the Diameter of the Dish. However, the result is the Cutting RADIUS as with the original program because it will be easy to build thinking about the radius. I don't know how in the USA you calculate the diameters because I saw foot and cm equally. I personally think in cm., but this it up to you (in the original article main calculations are done in cm.).
Also, I have added a "Press a key to end the application" (Lines 144 and 145) to avoid ending the program with just the result. This way would be easier if the program closes inmediately after the result, because I don't think you'll run the program on some old computer (although you may, too
).
So no more speak, here is the modified program in an executable format:
-
the Linux (compiled) version: http://usuarios.lycos.es/telefrancisco/plyweb/plywoodl
(If you do use the Linux version, do a chmod +x (or chmod u+x) inmediately after downloading the program, thanks
).
-
the DOS version:
http://usuarios.lycos.es/telefrancisco/plyweb/plywoodd.exe
-and
the Windows version:
http://usuarios.lycos.es/telefrancisco/plyweb/plywoodw.exe
This is all for today.
I want to thank the
FreeBASIC team for helping me (specially with the LOG "problem"
)
Also, thanks to the
BCX Developers for helping me (specially in the code to end the program just when a key is pressed)
And, of course thank to you all that have at least opened the post
and accepted me besides of being European
.
Finally, may I ask, although have asked in the first and third post: anyone haves access to: "Electronics & Wireless world", August 1989, as it's is supposed there is another article on this topic?
Thanks in advance for the possible replies, or, at least, for reading me
