I've been thinking about the matching network. I am now leaning against the method of generating CP in the article I linked as it is going to make it very difficult for me to match the impedances. I plan to go with the 90 degree phase shift method and feed them as two separate Yagis. To...
Some NEC code
Single Yagi Simulation
SY DIAM=.0174845 'Wire Diameter
SY R=.991474 'Reflector Length
SY RO=.4114 'Reflector Offset
SY DR=.956505 'Driven Element Length
SY D=.909194 'Director Length
SY DO=.4114 'Director Offset
GW 2 9 -RO -R/2...
Dave, these would be straight dipoles, but the article I linked in my original post describes an unorthodox method of generating circular polarization where you use perpendicular elements of the cross polarized Yagis.
Baluncore, I wouldn't say that I'm happy with 12 ohm impedance, but I assume...
I'm still a bit confused about what the antenna's impedance will be though. The article assumes a 50 ohm impedance where I simulated my Yagi at more like 12 ohms. I would also think that putting my antennas in the configuration described in the article is going to affect their impedances.
Thanks Baluncore. I assumed that independent orthogonal Yagis would not effect each other's impedance much. However, that article I linked describes a non-traditional way of generating RHCP where you feed perpendicular components of the driven elements in parallel. I'm not sure how this will...
I'm designing a cross yagi as one component of a capstone project. The design I have right now is 3 elements per polarization, counting driven elements (total of 6 elements). I ran a quick 4nec2 simulation of a single polarization (3 elements) using center excitation on the driven element and...
I've been busy the last couple weeks and forgot to come back here and write a reply. emi_guy, I'm literally drooling over the documentation that you posted. It's interesting how they are simultaneously broadcasting two different frequencies. I guess that the tower acts as a 1/8 wavelength...
I do not think that WLW uses a counterpoise. Nothing is visible above ground except the large coax cable feeding the antenna. I believe that it is properly grounded. See Fig. 8 of the patent I posted above (message 1).
So, essentially, the reason that the tower was made with a single contact point was so that the two balls shown here could simply rotate on top of each other, freeing the ceramic insulators from the torsion stress? How is it that modern towers get around this issue? Is it just better insulators...
berkemen, I was under the impression that it was actually a monopole. Perhaps you could think of it as a dipole, however, if the Earth acted as the second part - sort of an application of method of image charges. I think that this is a valid way of thinking about it.
Thanks for the replies everyone!
0xDEADBEEF, the patent definitely does stress the advantages of the single contact point with the ground - but I can't help but feel that it is a bit exaggerated. I can't imagine that a tower with three points contacting the ground would leak much more...
The tower itself actually is the radiator! The relatively long wavelength of AM radio makes for some very interesting size requirements. If you read through the patent, he actually talks about ways to improve the conductivity of the joints between each beam. Item 40 is just a rod which can be...
I grew up not far from WLW and it's giant diamond antenna mast. picture These Blaw-Knox antennas were extremely popular in the 1930s. I always wondered why the diamond shape. I found the original patent here, but it really doesn't say specifically why the diamond shape was chosen. It looks like...