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Build Your Own Antenna - Discuss topics for building your own antenna.

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  #21 (permalink)  
Old 05-05-2013, 3:40 PM
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Thanks for quick answer - I appreciate the input. For now, I'll just be using it with my HT. I guess, I will need to look at something a little more robust when I get my mobile.
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  #22 (permalink)  
Old 12-29-2017, 3:27 AM
   
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Smile Flowerpot antenna calculation for RG-59(75 Ohms)

I was not able to get hold of RG-58 cable but I have RG-59 which has impedence of 75 Ohms. Can anyone tell me how are these value of turns and length of shielded and unshielded path calculated?
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Old 12-29-2017, 7:53 AM
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You can't use 75 ohm coax to make a 50 ohm antenna.
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Old 12-29-2017, 5:55 PM
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Quote:
Originally Posted by hertzian View Post
I'll bet that if one were to put these on a test-range, you'd see the rough equivalent performance to a quarter-wave ground plane antenna. The slight amount of common mode current on this antenna tends to raise the elevation angle.
That's probably the reason you do not see this kind of antenna being sold. A 1/4 wave GP is less in heigh and more efficient with a low elevation angle pointing at the horison, a 5/8 GP even more so. Users that have restrictions to put up antennas would probably not gamble with a stealth antenna and get exposed to breaching their contract and finding themselves out on the street with their possesions.

Good description of the project though.

/Ubbe
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Old 05-13-2018, 12:37 AM
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That's because there is nothing to sell -- mostly trying to make something useful out of what you have on hand.

The choke isn't perfect, but is is waaay better than the usual "fold the braid back down the coax" method, which doesn't really serve as a sleeve at all, and couples into all the rest of the transmission line braid anyway.

It's one of those "I need to make an antenna, and all I have is a hunk of coax, with no access to niceties like brass tubing, chokes, radial wires etc." Perhaps like those guys in Alaska with no radio outlet close by
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