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The 5/8-Wavelength Antenna Mystique by Donald K. Reynolds

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  #17  
Old 03-13-2012, 10:57 AM
BOOTY MONSTER
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LOL , i didn't get the memo

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Old 03-13-2012, 11:03 AM
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Those antennas you mentioned are current-fed so current should be highest at the feed point, diminishing more as you go away from that point toward the ends of the half wave or car body.

A bottom-fed 1/2 wave is voltage fed and that's why the feed point impedance is so high, around 2000-5000 ohms.

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Old 03-13-2012, 03:53 PM
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Quote:
Originally Posted by BOOTY MONSTER View Post
since the merlin base antenna and most mobile antennas are less than 7 ft tall above their feed-point ...... does that mean the current is highest 2 feet (or lower on shorter verticals) below the feed-point on the ground planes or car body ?
does it mean when my 3 ft lil will in on the 6 ft high roof on my vehicle that the current is highest just under the tires ? if it were on a trunk , would it be 3 ft under ground ?
Your reasoning here is silly, and you missed NB's point completely. Go sit in the corner and put on the dunce cap.
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  #20  
Old 03-13-2012, 04:02 PM
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can you explain why it's silly and what point i missed ?
BTW , i'm always in the corner wearing my dunce hat

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Old 03-13-2012, 04:02 PM
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Quote:
Originally Posted by Marconi View Post
Your reasoning here is silly, and you missed NB's point completely. Go sit in the corner and put on the dunce cap.
LOL!

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Originally Posted by BOOTY MONSTER View Post
can you explain why it's silly and what point i missed ?
BTW , i'm always in the corner wearing my dunce hat
Is that the one you stole from me? - HEY, I need it BACK!

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Originally Posted by Needle Bender View Post
isn't the current highest about 1/4 wave down from the top?
I was referring to the 22 1/2' 5/8 wave Marconi had modeled.

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Old 03-13-2012, 04:28 PM
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i earned the dunce hat today
you can have it back when you earn it

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  #23  
Old 03-13-2012, 07:20 PM
BOOTY MONSTER
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from OGP's link
G3ZPS HF radio antennas

"The 'Zepp' name came from the use of the antenna on Zeppelins in the 20's and 30's. Its a non resonant antenna which provides arounnd 3dB of gain over a dipole if mounted at the right height. Around 0.6 of a wavelength is ideal .


Each leg of the Zepp is 0.64 Wavelength (5/8) and must be fairly accurately cut, the formula I use is 599/f in MHz."


i thought antennas were supposed to always perform better when they were resonate . and this one is supposed to have more gain over a dipole than a 5/8 or .64 . the formula looks to be a bit shy of whats commonly thought of as a 5/8 WL , let alone a .64 .

599 / 26.965 = 22 ft 2 1/2 inches for channel 1
599 / 27.405 = 21 ft 10 1/4 inches for channel 40

it ain't easy being a dunce

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  #24  
Old 03-14-2012, 02:02 AM
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Quote:
Originally Posted by BOOTY MONSTER View Post
from OGP's link
G3ZPS HF radio antennas

"The 'Zepp' name came from the use of the antenna on Zeppelins in the 20's and 30's. Its a non resonant antenna which provides arounnd 3dB of gain over a dipole if mounted at the right height. Around 0.6 of a wavelength is ideal .


Each leg of the Zepp is 0.64 Wavelength (5/8) and must be fairly accurately cut, the formula I use is 599/f in MHz."


i thought antennas were supposed to always perform better when they were resonate . and this one is supposed to have more gain over a dipole than a 5/8 or .64 . the formula looks to be a bit shy of whats commonly thought of as a 5/8 WL , let alone a .64 .

599 / 26.965 = 22 ft 2 1/2 inches for channel 1
599 / 27.405 = 21 ft 10 1/4 inches for channel 40

it ain't easy being a dunce
Well, since the Germans probably used insulated, braided wire for strength & shorting resistance, I bet the velocity factor made it electrically longer than .6, perhaps .64?
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