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Roy W7YRV/SK developed the X Rhombic

Updated: Apr 27

From Roy web site

Roy W7YRV/SK had nine at one time and he developed the X Rhombic, which he had one for every 20 degrees. That was a truly remarkable accomplishment for an amateur station (You must see his page, great info w7yrv.blogspot.com/2013/). It was an extreme pleasure for K0UO to meet Roy, even in his 90's, he was still an encyclopedia of knowledge when it comes to very high gain antennas. K0UO is very privileged that W7YRV has entrusted him with the schematics, drawing, and photos of these fabulous antennas.

K0UO's Curtain Array with Distributed-fed is using the W7YRV "X" rhombics desing . It is a traveling wave antenna, which is a non resonant traveling wane antenna. The rhombic antenna can radiate at elevation angles close to the horizon, and is called a Traveling wave or a Leaky-Wave Antenna (rhombics are fast wave), with a phase velocity greater than the speed of light. This type of RF wave radiates continuously along its length, and hence the propagation wave=number kz is complex, consisting of both a phase and an attenuation constant. A highly directive beams at an arbitrary specified angle can be achieved with this type of antenna, with a low sidelobe level. The phase constant of the wave controls the beam angle (and this can be varied changing the frequency, while the attenuation constant α controls the beamwidth. The aperture distribution can also be easily tapered to control the sidelobe level or beam shape. Leaky-wave antennas can be divided into two important categories, uniform and periodic, depending on the type of guiding wire cable structure.

Nine rhombics antennas (reconfigured)

Three 1100 foot long rhombics 120' high and the control relays giving you six direction. I used these antennas for about 18 months until I figured out how to put 9 of them on my 40 acres.

 

 

 

 This is the relay control box that takes the power to one end of the rhombic antenna and then brings back the reflected power to the shack to be terminated making the antenna transmit only in one direction. The four deck wafer switch allows me to select any of the six directions.

 

                               



Nine  rhombics antennas reconfigured. You cut a diamond shaped rhombic in half, and then put it back together in the form of an X, and feed it in the center, now you have  electrically the same antenna. These rotating  rhombics change directions in 20 degree steps, and they cover all bands from 160 through 10 meters.  The apex angle can be adjusted from 40 degrees on the high bands to 120 degrees for the  low band. Of all the antennas I have built, this was the best all around antenna.  If I had to do it over again, I would have made them 120 feet high to get a little lower angle of radiation, but at 65 feet it was a super  great performer.  When I started building 197 foot towers for the 80 meter sterba curtains, the center tower of this antenna system was in the way, so although it grieved me to remove it, I knew that if the 80-meter antenna system didn’t work out, it would be no big deal to rebuild it.



Above, 120' feet of 3 inch pipe, to be a tower for the 20 meter sterba curtain. The 50 foot triangular tower section on the truck has the 120' tower wired to it, in order to keep the ends of the pipe off the ground.

The reconfigured rhombic antenna system with the transmission lines coming down to ground level. Ever thing worked very well, so later we moved the relay box to the top of the tower




Below,This is a 40' gin pole pulling up a 65' rhombic tower.





We moved the relay box to the top of the tower


The 600-ohm transmission line goes to the relay control box that is connected directly to the antenna system. 



This is a Gila monster that I almost stepped on.  I heard a loud hiss, and I jumped a few feet, at first; I thought it was a rattlesnake. I just had to get a picture of him, because you almost never see one in the daytime.





The direction control box with a 9-position switch that lights up four lights on each of the 9 antennas showing you the direction and apex of your antenna.  

It, looks complicated but its not, each deck is for a different apex.




 This is the relay switching box at the base of the tower 







 The transmission lines coming down to the relay box. The antennas performed great with the relay box at ground level, 




    A look inside the relay box.  The wires seem to be going everywhere. You might think you could have an impedance problem, but it was not apparent.

Posted by Roy at 8:41 AM

2 comments:

  1. K0UOJune 25, 2018 at 10:17 AM I talked to you a few years ago after I got my rhombic system working here in Kansas I really appreciate design information you have on the your old system. I especially like the feeding from the center X design rhombic I wished I could have thought of that before I installed these three big ones here in Kansas that I have. Reply

  2. K0UOApril 30, 2019 at 6:44 PM I JUST WANTED TO SAY, THANK YOU ROY.After meeting you in Jan 2019 I have been able to use your X Rhombic design to build a Distributed-fed Curtain by stacking two X-Rhombics at 190foot and 100 foot,and it is a steerable design. The antenna is also using Roy's old outside control_box(rebuilt) that you see in this blog. Reply


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