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The 5/8-Wavelength Antenna Mystique by Donald K. Reynolds
- Thread starter Marconi
- Start date
B
BOOTY MONSTER
Guest
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.
A bottom-fed 1/2 wave is voltage fed and that's why the feed point impedance is so high, around 2000-5000 ohms.
Your reasoning here is silly, and you missed NB's point completely. Go sit in the corner and put on the dunce cap.
B
BOOTY MONSTER
Guest
can you explain why it's silly and what point i missed ?
BTW , i'm always in the corner wearing my dunce hat
BTW , i'm always in the corner wearing my dunce hat
LOL!
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! :tongue:
I was referring to the 22 1/2' 5/8 wave Marconi had modeled.
B
BOOTY MONSTER
Guest
B
BOOTY MONSTER
Guest
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
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
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? :bdh:
NB and BM, what was G3ZPS referring to when he said, "Around 0.6 of a wavelength is ideal."
Well, there he's referring to height above ground, but I find the following sentence rather humorous:
"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"
.64 is not "accurately" .625 or 5/8, neither is 599/freq mhz :mellow:
I think that .599 is about as accurate as needed really. About like .64 being better than .625 sort of. Accurately cut would probably be the relationship between the two halves of that antenna, not the exact length. I don't think it would have been used on any -one- frequency, but the whole band. So, once you move from the design frequency it's gonna be 'off' a bit anyway. That would be a little more important since it's a balanced antenna using a balanced feed line (ideally).
There's always some 'skootch' involved with HF antenna lengths. Just one reason is that height and environment plays a bigger part in resonance than on the VHF/UHF bands. At HF you're talking about 'foot' accuracy, where at VHF/UHF you're talking about small fractions of a 'foot'.
- 'Doc
(Besides, it probably looses something in translation between American English and Her Majesty's English. You think?)
There's always some 'skootch' involved with HF antenna lengths. Just one reason is that height and environment plays a bigger part in resonance than on the VHF/UHF bands. At HF you're talking about 'foot' accuracy, where at VHF/UHF you're talking about small fractions of a 'foot'.
- 'Doc
(Besides, it probably looses something in translation between American English and Her Majesty's English. You think?)
Well, I don't mean to put words in your mouth, but it seemed strange to me that you guys were talking about antenna length in reference to the .6 idea presented by G3ZPS. I didn't read it that way, and it caught my attention that maybe there was some more CB BS on the rise.
I was wondering about BM's statement below, and then your response seemed, to me, you too were referring to a radiator length of .6 wavelength as being optimum.
Now I also suspect that 'Doc read your words as if you two were both talking about radiator length in reference to the .6 wavelength number. It is hard to excuse the facts in print, and at times I do the same myself.
I posted this additional link to provide BM with some evidence that there are Internet references to .64 wavelength raditors...where it shows big gains for Ham operators far back in History. I sometimes suspect that much of the CB BS we hear and read about...originates from just such historical accounts where guys take stuff out of context.
B
BOOTY MONSTER
Guest
NB mentioned a .6 radiator , i'm guessing because he did the math using the authors formula and saw that the mats showed it to be closer to .6 wavelength . if i'm wrong on that NB then correct me and accept my apology .
but i never said anything about a .6 wavelength radiator , the author mentioned .6 in reference to height . the link was posted FWICT to support the .64wl idea . but the formula used didn't come up to that length . the author didn't say what wire he used so we don't know if it was jacketed or not . i guess i'm thinking since the antenna wasn't really .64 wl long that it doesn't apply as a example of the .64 .
i didn't notice any difference (for or against) on my 5/8 between a 22 1/2 ft vertical or a 23 ft vertical , but i'm a fan of someone doing something just for the warm fuzzy feeling it gives them , if it doesn't cause any negative effects .
hi guys. interesting topic for sure. ive always wondered if the imax 2000 and a99 antennas were the wire lenghts just happen to fall at the right wave lenght size everytime ? how could this be possible? is there something iam missing? because surley you would have to take into account the vf of the wire used AND it being encapsulated!!!! yet it still has the right lenghts for said antennas! ie 18 and 24 foot !!! 73s.