Cellular (800Mhz) antennas/boosters?

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CeaSaR
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Re: Cellular (800Mhz) antennas/boosters?

Post by CeaSaR » Sat Nov 28, 2009 8:16 pm

Came across an article on making a dipole reflector antenna in one of my old magazines. If you are interested, let me know.

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kheston
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Re: Cellular (800Mhz) antennas/boosters?

Post by kheston » Sun Nov 29, 2009 10:37 am

Ceasar,

Still in research mode. So far, I've only managed to experience the continual frustration of not having built a better antenna.

I have a modem for data and a Motorola Droid for voice. I'm looking for TNC connectors/adapters at the moment. Surprisingly, given the ubiquity of cellular tech, my local retailers (Fry's, Radio Joke) don't sell them. Prices for ones online look reasonable.

From what I'm reading, it looks as though I can go quite a few feet using standard RG6 without it becoming a problem, so that's good. I have a height issue I need to solve, too, and towers look ridiculously expensive. I've got lots of tall pines (50-75ft) around me and am wondering whether I can use them in conjunction with a long mast to poke above the tree-top. Perhaps hanging an antenna in the center of a tether between two of them might work as well.

Can I buy a reprint of the article you found somewhere?
Kurt - SF Bay

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CeaSaR
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Re: Cellular (800Mhz) antennas/boosters?

Post by CeaSaR » Sun Nov 29, 2009 10:43 am

How about a scan? The magazine is defunct and you probably won't be able to find it. I have scanning to do later,
so I could send it to you if you want it. PM me w/your addy.

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Bob Scott
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Re: Cellular (800Mhz) antennas/boosters?

Post by Bob Scott » Sun Nov 29, 2009 2:48 pm

I'd like to see that dipole with a reflector too.

Let me guess. It is a dipole with a slightly longer reflector element just behind the dipole?

Now if you add some directors that are shorter than, and in front of, the main element, you'll have a Yagi. For half wave of 800MHz, the half wave element length is 7"?

I wait in anticipation to see how wrong I am. Some of the newer bow-tie TV antennas have a single reflecting mesh ground plane behind the main elements.
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CeaSaR
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Re: Cellular (800Mhz) antennas/boosters?

Post by CeaSaR » Wed Dec 02, 2009 8:28 pm

Ok guys, I'm back. I did one better than scanning the article, I found the original owner's website.
You can can find William Sheets, K2MQJ, and Rudolf F. Graf, KA2CWL, at North Country Radio.
This page is the gateway to the beginning of the article on the UHF corner reflector antenna. I'm
sure that with the other info I pointed you to, you'll be able to calculate the correct dimensions.

Bob, I think this will give you the answer to your, as Frank-n-Furter from Rocky Horror Picture Show
said, "...antici..............................pation!". Yes, completely on the wrong track. Not a bad track,
mind you, but just not the same one shown here. :mrgreen: Although you almost hit it with the TV
antenna description.

Enjoy!

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Bob Scott
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Re: Cellular (800Mhz) antennas/boosters?

Post by Bob Scott » Thu Dec 03, 2009 9:40 pm

CeaSaR wrote:Ok guys, I'm back. I did one better than scanning the article, I found the original owner's website.
You can can find William Sheets, K2MQJ, and Rudolf F. Graf, KA2CWL, at North Country Radio.
This page is the gateway to the beginning of the article on the UHF corner reflector antenna. I'm
sure that with the other info I pointed you to, you'll be able to calculate the correct dimensions.

CeaSaR
Thanks Ceasar. That looks cool and should have some gain.

Just some observations: I bet it would have higher gain if, instead of having a sharp 90 degree corner reflector, had a parabolic cross section with the antenna at the focus. Just bend the aluminum reflector sheet metal into a 2 dimensional parabolic curve with your hands, or a pie dough roller.

Instead of that slotted brass pipe used as a balancing device, I'd try directly hooking the coax up to the antenna and install a ferrite bead around the coax right at the antenna end. In effect, the bead would act as a one turn coil. (Any pass through the middle of a core counts as one turn.) The coil acts as a common mode filter, stopping the coax from being part of the radiator as described in the article. I think the driving impedance of a half wave dipole is 75 Ohms, no?

The ferrite material type would have to be good for 800 MHz.
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Re: Cellular (800Mhz) antennas/boosters?

Post by kheston » Wed Feb 24, 2010 8:40 pm

Any coax cable recommendations? A bit of Google searching has shown RG8 and LMR400e as options, but I know little about what makes one cable type better than another.

I was considering using a 20ft pole initially and perhaps going as high as 100ft (provided I can find a decent tower on Craigslist for sale) later. I'm wondering whether the LMR400e coax is worth a buck a foot. Ideas?
Kurt - SF Bay

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Re: Cellular (800Mhz) antennas/boosters?

Post by CeaSaR » Thu Feb 25, 2010 12:44 am

Apparently RG6 is good to 1000 MHz. Link Only thing is, it is 75 ohm. Of the other 2, the
descriptions suggest that the LMR400e is lower loss than RG8. Anyone else have an idea?

How's the antenna? Did you try one yet?

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