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Old 30-Jun-2012, 9:44 PM   #1
vienna01
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Need Help Assemblng Log Periodic TV Ant

As the title suggests, I really need help figuring out how to CORRECTLY assemble my TV antenna When I ordered it I expected to do some assembly, but all I got were parts. I decided to take on the challenge [a mistake]. The list of parts shows UHF dipole completely assembled !

In the attached photos/diagrams I show both some of the instructions that came with the “antenna” and some photos that I made.. From my experience 5 decades ago [true], I think this is called a log periodic antenna. I recall it would have active and reflector elements. The cover of instructions says: ” Two directors, two dipoles good receptivity”. UHF 21-99 470-860 36 Gain {db} impedance (ohms) 75.”

There are only three sizes of aluminum pipe loops. All the plastic parts that support the aluminum loops are identical for all three sizes. In my TRIAL assembly, I have only made the large loops touch [join]. The Large Loop is at the rear of the antenna.

I made only the large loops touch without any particular reason. For all the Small loops and the Medium loop, the 2 opposing aluminum pipe loops are not joined –they do not touch. These are about 2 inches apart.

I guessed that the medium sized loop was the active part of the antenna and the others were reflectors. There were 2 thin flexible metal strips that came out of the center rotator assembly [black plastic marked UHF]. I attached one of each metal strip to each side of the aluminum loops. The two sides of this Medium Loop are not joined-they are not connected,

The antenna has a rotor housing that might also include some electrical components. The rotor has a twin-lead type cable marked VHF and to metal strips on the other side marked UHF. The antenna came with a combined power supply booster that is to be connected to a 50 foot coax cable that is connected to the rotor. The power supply booster combo has three coax connectors marked, antenna, DVR and television. It has an on-off switch and a button that causes the rotor to turn. The antenna turns 360 degrees and then reverses itself.

My questions:

Which of the Small. Medium and Large Loops, if any, should touch in the center?

Should all the loops be isolated from the center square pipe?

If any of the loops need to be joined in the center [to form a closed loop] should I add a bit of wire to make sure they are well connected [joined in the center]?
Even when they are joined, they might separate a bit in the wind.

Should the metal strips be attached to the medium or to the large loop [I can do it either way ?
Attached Images
File Type: jpg 500-medium-loop-w-strips.jpg (81.4 KB, 347 views)
File Type: jpg 500-small-manufact-instruct#1.jpg (39.4 KB, 361 views)
File Type: jpg 500-small-loop-at-front.jpg (67.4 KB, 314 views)
File Type: jpg 500-small-instructions-#2.jpg (47.1 KB, 357 views)
File Type: jpg 500-small-Extra-View-How-Al-Strips-Attached.jpg (79.0 KB, 325 views)
File Type: jpg 500-small-looking-toward-front.jpg (91.5 KB, 336 views)
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Old 30-Jun-2012, 11:15 PM   #2
GroundUrMast
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It looks like you have an antenna that's marketed under several brand names, Orca & Lava being quite common. Sadly this antenna and it's variants have a poor reputation. Common complaints are like yours, poor or non-existent documentation & support. Other common reports cite poor construction and durability problems. Finally, the advertising claims of extreme long range performance are often challenged by real world experience.

That said, I don't think the elements are supposed to touch at the center. I'm basing that conclusion on advertising photos of the product... I won't waste my money on this type antenna.

Still, I wish you success. Some users have been able to get acceptable reception with this type of antenna.
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Old 1-Jul-2012, 1:26 AM   #3
vienna01
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I wasn't expecting much. My former rotor Alliance Tenarotor was 50 years old!
I have a yagi antenna that was state of the art then on the Old Alliance. I haven't seen the control for it for about 30 years. The reason I didn't connect the small and medium sized loops was looking at the diagrams and the box. Am I correct that the medium loop is the only active one? Should it be joined at center? Should all others not be joined at center? Maybe the active element shouldn't be joined either.

I have just looked around the net a very little. I'm guessing that the loop designs are called dipoles. I don't know what an antenna with many of these should be called.
I'll have to do some more searching.

THANKS FOR YOUR RESPONSE

Last edited by vienna01; 1-Jul-2012 at 1:39 AM.
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Old 1-Jul-2012, 2:04 AM   #4
GroundUrMast
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The only active element that I see is in the first photo, "...medium-loop-w-strips...".

I don't believe the left and right element sections are supposed to make contact with each other.

FWIW, this does not appear to be a log-periodic, but rather a Yagi-Uda style design.
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Old 1-Jul-2012, 3:00 AM   #5
vienna01
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Quote:
Originally Posted by GroundUrMast View Post
The only active element that I see is in the first photo, "...medium-loop-w-strips...".

I don't believe the left and right element sections are supposed to make contact with each other.

FWIW, this does not appear to be a log-periodic, but rather a Yagi-Uda style design.
Yes the only element that I connected to the plastic housing [rotor] is the medium loop.

I have found 2 antenna pictures [China] that are similar I'll attach them. One seems to have its long element behind the big reflector. These photos don't help me though.

I found the following reference on Yagi-Uda style antennas. Seems very much like mine except the article example uses single pipes where I have loops.
http://www.antenna-theory.com/antenn...lling/yagi.php

It calls the only active element a folded dipole and calls the element in the back a reflector. The other elements are called director elements by the article. It doesn't speak about a element in the very back like mine[the wire mesh circular one].

I think that with your reply and the technical article I know what to do with
The small loops [directors], the medium feed loop[folded dipole] and the large loop[reflector].
THANKS
Attached Images
File Type: jpg ant a.jpg (45.2 KB, 564 views)
File Type: jpg ant b.jpg (16.8 KB, 346 views)
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