Canadian TV, Computing and Home Theatre Forums - View Single Post - Introduction to the Gray-Hoverman TV Antenna (the original thread)
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Old 2008-01-13, 01:42 PM   #19
oneoldude
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Join Date: Jan 2008
Posts: 5
Default Hoverman impedance matching (long)

Hi guys, I'm a lurker/new member and have read lots of good stuff here but I need some help. I hope you don't mind the length of this post.

The Hoverman seems like a great DIY project and I am going to build it. But there is a problem.

In the days of 300 ohm inputs and 300 ohm flat twin lead, a single Hoverman was a perfect match for the TV imputs of the day. But that was then and this is now (75 ohm).

From what I understand, using a balun to impedance match results in a very large loss of signal at UHF and in effect defeats the benefit of a good antenna design like the Hoverman. Also, home made baluns made from shielded lead are bandwidth limited and will impede the wide bandwidth features of the Hoverman. There must be a better way.

I was thinking that by paralleling four Hovermans the resultant impedance would be 75 ohms and there would be no need to impedance match at all. I could then go direct to 75 ohm shielded lead and be done with it. So my first question.... Is that true?

My second question is what kind of problems would exist with that kind of a set up? In other words how should the array be wired so as not to screw up the natural benefits of the Hoverman?

I did a bit of surfing and found the following antenna. It seems to be a double Hoverman (It sure would be nice if somone could model and optimize this design with dimensions provided to all!)
The website where I found the pic does not describe the impedance of the pictured design. So now to my third and fourth questions. Is it 150 ohms? Can it be made a native 75 ohms?

My fifth question is how would one connect two of them to get phasing right, not interfere with the fundamental antenna design and get down to a 75 ohm impedance? Is a simple parallel connection the right way to go?

My last question is about an active impedance match. Are there any VHF/UHF or UHF antenna amps out there that have high enough input impedance that they can be used for an antenna with any impedance (300 or 150 or 75 ohm) and still provide a clean 75 ohms out for modern TV (or HDTV) inputs? If such an amp existed I could build any version of the Hoverman and still get a good match at my shielded cable and RF inputs.

Suggestions? Comments?

Thanks
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