The latest QST has an interesting EDZ beam. It has a discontinuous reflector,
actually two reflectors, one for each half. William Alsup, N6XMW, modeled it
with EZNEC. The model predicts 6 dBd. That is pretty wonderful but the antenna
takes a heck of a lot of space.
A plain old EDZ is dang fine antenna. I ran one on 15M some number of sunspot
cycles ago. I could work Japan without even turning the transmitter on,
actually without even entering the shack. It was that good.
Jon
On Sep 15, 2014, at 12:04 PM, Bob McGraw - K4TAX wrote:
> In review of the ARRL Handbook, Ed. 2014, Chapter 21.7, there are clearly two
> distinct examples of Zepp antennas. One being 1/2 wavelength and end fed
> with open wire line and the 2nd being a center fed 1/2 wavelength wire fed
> with open wire line.
>
> On page 21.7 we find: "Another variation, shown in Fig 21.12B, is the end
> fed Zepp, named for it original application as an antenna deployed from
> Zeppelin airships. The feed point impedance of a Zepp is quite high,
> requiring open wire feedline and impedance matching techniques to deliver
> power effectively."
>
> The Extended Double Zepp is described as having an overall length of 1.28
> wavelengths which equates to 0.64 wavelength on each side of the center
> insulator and feedpoint. This antenna is reported to have ~3 dB of gain to
> its broadside. The length of the wire antenna is calculated as: 984/f(MHz) x
> 1.28 = length in feet. The feed point impedance is ~140 ohms using wire
> elements.
>
> I find it interesting to examine the dipole antenna. By definition it is a
> wire length being equal to 1/2 the wavelength of the frequency. The name
> comes from two terms "DI" meaning two and "POLE" meaning electrical terminal
> having two distinct regions of electrical polarity. A dipole is resonant
> when it is electrically 1/2 wavelength so that the current and voltage in the
> same antenna are exactly 90 degrees our of phase. The length of a 1/2 wave
> wire dipole is calculated as: 468/f{MHz} = length in feet. The feed point
> impedance of a 1/2 wavelength horizontal dipole varies with height above
> ground. The feedpoint impedance will vary from a very low value, 20 to 45
> ohms over average real earth, when the antenna is less than 0.1 wavelength
> above ground to near 100 ohms at ~0.34 wavelengths above the ground. At
> heights greater than 0.34 wavelength the impedance will typically be 75 ohms
> +/- 5 ohms. The nominal 75 ohm value will be found at heights of 1/2, 3/4,
> and 1 wave
length above ground.
>
>
> 73
> Bob, K4TAX
>
>
>
> ----- Original Message ----- From: "Marty Hartwell" <mhartwe@gmail.com>
> To: "Ten Tec list" <tentec@contesting.com>
> Sent: Monday, September 15, 2014 10:49 AM
> Subject: [TenTec] Zepp
>
>
>> Hi
>>
>> I was reading the posts concerning the Zeppelin antenna. I did a search on
>> the web
>> and got some picture drawings showing what I am familiar with. Also someone
>> said it was a trailing wire antenna, which is one I used from a bomber type
>> in
>> the Navy, which is simply a spool of wire attached to an automatic matching
>> device
>> and the wire is a random length, to install it we just strung out what we
>> estimated to
>> be over a 100 feet, no real measurement done. In some cases we were able to
>> get
>> a type of wire that was reinforced but usually it was just plain old 14 gage
>> wire we
>> were able to pick up at a hardware store or some such.
>> Yes Zeppelins may have used a trailing wire antenna I know our Blimps during
>> and after
>> WW2 had them, but the Zepp used on the Zeppelins was supported in each end
>> of the
>> main straight part of the top and fed with open wire feeder, and the feeder
>> was whatever
>> it took to reach the tuner/matching device.
>> To the persons saying it is a G5RV antenna, it is not, the G5RV radiator is
>> of a specific
>> length, and has a fixed length for the 75 Ohm feeder, if I remember right. I
>> have used
>> a Zepp antenna, but not a G5RV.
>>
>> Marty kd8bj
>>
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>
>
>
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