Thread: Rca ant751
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Old 25-Jun-2017, 4:04 PM   #82
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
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Originally Posted by OTAFAN View Post
I have another question regarding the tetrapole on the RCA751 as to how it would correspond to an LPDA antenna such as AD Element.

I think I understand better now how it works on the 751, but how does an LPDA separate and combine UHF/VHF signals?
The Tetrapole on the RCA ANT751R has two functions. First, it is the driven element (DE) for UHF signals. Second, it acts as a UHF/VHF combiner (UVSJ) in conjunction with the shorting stubs. There is no need for a UVSJ on the AD Element Antenna; it is designed for continuous coverage of UHF and VHF-High. What is curious is that a UVSJ is suggested as an accessory for the Element on the AD site. It would be useful if you only wanted to use the Element for VHF-High and have a separate UHF antenna.
I have reread a Wikipedia article on the LPDA and it seems to me that it may have something to do with the fact that the dipoles are electrically connected directly into the boom(s) rather than the cross phased elements in the 751.
The LPDA can be constructed either way. It can have two booms that are insulated from each other that also act as phasing lines to connect the elements together, or it can have one boom with the elements mounted on insulators and wires to connect the elements together. The two ways are electrically equivalent, but physically different.
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File Type: jpg AD Element Ant1.jpg (77.8 KB, 2618 views)
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Last edited by rabbit73; 25-Jun-2017 at 4:11 PM.
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