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 Post subject: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 4:56 pm 
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Location: North Providence, Rhode Island
I just purchased a HD over the air broadcasting antenna and now that I have it I am having second thoughts. While putting it together the figure 8 elements on the antenna were attached to the straight aluminum piece with metal screws but the black plastic part of each element is just that, plastic. So how does it make contact? Should it make contact? Are they just for show?


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b8e28372-15b6-491d-aa8f-38a7151b2efb_1.6af3cbb1d0823eb2e3a624c5515ae2c5.jpeg
b8e28372-15b6-491d-aa8f-38a7151b2efb_1.6af3cbb1d0823eb2e3a624c5515ae2c5.jpeg [ 29.3 KiB | Viewed 726 times ]

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 5:58 pm 
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I understand your skepticism. I don't know the answer but I can contribute this.

The Yagi calculator I use has inputs for bonded and nonbonded elements, and for metal boom and non metal boom. The four different combinations result in four different antennas. But the dimensions don't differ by much. That makes me think it is possible that your antenna works.

I've never seen one like it, and it may indeed be a bunch of hooey. Then again, UHF antenna design is close to black magic. How well does it actually work?


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 6:05 pm 
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Location: North Providence, Rhode Island
Thank for your help. It's sitting on my dining room table so time will tell. It's kind of cold in New England so it may be some some before I try it.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 7:32 pm 
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Can you post a link to the vendor from which you bought the antenna? I am hoping to get a look at the antenna from different angles.

What I notice is that the proportions of the sizes of the different elements is unusual. The long folded dipole element appears to be cut for high band VHF (which would not be unusual). However, the reflector screen and "directors" appear to be cut for UHF. I have used quotation marks because I don't know whether Yagi directors can work correctly when they are cut in half.

What I can say from looking at your photo is that this antenna will perform almost like a dipole at high VHF. Depending on your surroundings, there could be multipath problems.


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 8:01 pm 
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Location: North of Mpls, Minnesota
Good pictures here.
https://picclick.com/Vhf-Uhf-Digital-Dt ... 62564.html

Dave


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 9:16 pm 
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Location: Georgia, 30236
I have an antenna like yours. I too don't know if the metal portion of those figure 8's contribute at all. The antenna though, has worked well for me.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 9:26 pm 
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It's listed several places on Amazon.
Read the customer reviews on its performance.

https://www.amazon.com/Amplified-Antenn ... 4006274011

Director elements on a yagi don't have to be mechanically and electrically connected to each other to support gain to the yagi.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 9:31 pm 
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arzoo623 wrote:
Thank for your help. It's sitting on my dining room table so time will tell. It's kind of cold in New England so it may be some some before I try it.

Nothing says that you can't try it indoors. place it near a window, aimed in the direction of a transmitter, and see how/if it picks up.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 9:42 pm 
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When I assembled mine, I tried it hand held standing in the living room. it worked substantially better than my amplified tabletop antenna. I now have it mounted on a torchiere lamp column in the attic. It has enough room to rotate and gets me most of the areas' OTA stations. It is pretty directional, so the rotor is a good feature.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 10:10 pm 
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Location: North Providence, Rhode Island
Glad to hear as I was thinking of putting mine in the attic.

Thanks

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Jan Wed 31, 2018 11:13 pm 
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It may depend upon the pitch of the roof, but the most distant stations drop out in heavy rainstorms. Mine has a low angle pitch and is one story above ground.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Thu 01, 2018 3:45 am 
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Location: East Brunswick NJ,USA
To answer the original question, those figure 8 elements do make the antenna more directional and have more gain and do not need to be "connected' This is how a yagi works. Only one element is wired and is called the "driven"element. This style of antenna is incredibly flimsy and wont hold up on a roof very long. Height is very important, but a lot depends on your distance from the stations try it in the house aiming it in different directions. have your TV do a channel scan each time you change directions and see what you get.
Marty


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Thu 01, 2018 7:02 am 
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Location: SoCal, 91387
First, there's absolutely no difference between a so-called "HD" antenna, and any other TV antenna.

If most or all of the stations you are trying to receive are in the UHF band, the tried and true 4-bay bow tie rig can't be beat, and you can build one yourself out of wire coat hangers and aluminum window screen material, if you don't want to spend for it.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Mon 05, 2018 3:52 am 
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If it is an actual yagi, the front elements do not need to be connected to the driven element. They are "directors". They interact electrically with the driven element, the one that is attached to the coax. They should be a tiny bit shorter or smaller than the driven element.

I once made a yagi out of wire, with one driven element (for CB) and two 'directors'. I got maybe 7 or more db of gain in the direction of the directors.


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Tue 20, 2018 2:17 am 
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Location: North Providence, Rhode Island
Well what ever it is I have to report that it worked great. I ended up putting it up in the attic.

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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Tue 20, 2018 3:51 am 
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Location: West Point, PA
manualman wrote:
It's listed several places on Amazon.

https://www.amazon.com/Amplified-Antenn ... 4006274011



I clicked on this link and ended up buying a GPS! LOL!!!


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Wed 21, 2018 9:07 am 
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I have been meaning to photograph the innards of a GE amplified indoor TV antenna and post the images here. This was an antenna that was purchased at a local department store for about $20 a few years ago. GE claims that the antenna's built-in amplifier offers 20 dB of gain, which seems unnecessary to me, since this antenna is made to be located very close to the receiver.

I was surprised by what I found when I opened it.

Here is the foil side of the board. The two brass bars make up the UHF portion of the antenna. It is a two element Yagi! The short element feeds the amplifier. The long element connects to RF ground through a surface mount capacitor (which may be there for tuning purposes).

The VHF rabbit ears are quite cheesy in that they do not feed a balanced input. One of them is simply connected to RF ground.

Attachment:
DSCN5333.JPG
DSCN5333.JPG [ 195.06 KiB | Viewed 145 times ]


Here is the component side of the board. Almost all that can be found here are inductors. L1 is in parallel with the VHF input to serve as a high-pass filter. L5 and L6, together with a shunt capacitor on the foil side of the board form a low-pass filter. The UHF antenna input is a mirror-image of the VHF circuit. In other words, input inductor L7 forms a low-pass filter, while shunt inductor L8 and two series capacitors on the foil side of the board form a high pass filter. The outputs of both filters combine at L9 (the spread-out coil). L9 might be there to improve impedance matching at UHF.

L13, L14, L12, and L15 all form traps. L16 and L17 are respectively in series with the input and output of the RF amplifier IC. My educated guess is that they assist in impedance matching at UHF.

Attachment:
DSCN5335.JPG
DSCN5335.JPG [ 215.54 KiB | Viewed 145 times ]


Finally, here is the foil side of the board. U2 in the center is the single-chip low noise RF amplifier. There are also some diodes to protect the inputs and the output from static discharge.

Attachment:
DSCN5334-smaller.JPG
DSCN5334-smaller.JPG [ 223.63 KiB | Viewed 145 times ]


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Wed 21, 2018 10:25 am 
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Location: Albuquerque, NM 87123
You bought an antenna that needs assembly????


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 Post subject: Re: HD Broadcasting Antenna
PostPosted: Feb Wed 21, 2018 1:49 pm 
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Location: Georgia, 30236
Yes. It works!

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