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Old 7-Aug-2019, 6:04 PM   #14
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,747
Quote:
Originally Posted by freetvplease View Post
rabbit73 from the picture you posted I can see that the 7511 is missing an element that the 751 has
That is correct. The VHF section is missing one director, the UHF driven element is a straight dipole instead of the Tetrapole, the 4 shorting stubs that act as a UVSJ have been replaced with a pair of thin wires, and the first director in front of the UHF driven element is a straight strip instead of a director pair.

The Tetrapole was invented by John Winegard, and he used side-by-side director pairs in his patent.





In the current 751E, they went back to the original design:



GroundUrMast is correct. The center of parasitic elements (director and reflector) can be attached to the boom because that is a zero voltage point; it doesn't affect the performance of a Yagi antenna.

However, the VHF section of the 751E is a hybrid design. The two rear VHF elements are a Log Periodic design that are connected together and then connected to the top of the UHF Tetrapole driven element where they are combined with the UHF signals. The front two VHF elements are parasitic Yagi director elements to increase VHF gain and can be fastened to the boom without harm. That is why the VHF section is called a Log-Yagi.
Attached Images
File Type: jpg RCA ANT751E_2.jpg (78.6 KB, 1764 views)
File Type: jpg WinegardPatentDirectorPairsRev.jpg (178.9 KB, 3665 views)
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Last edited by rabbit73; 7-Aug-2019 at 7:25 PM.
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