[TenTec] Zepp

[k6jek]

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 wavelength above ground.
> 
> 
> 73
> Bob, K4TAX
> 
> 
> 
> ----- Original Message ----- From: "Marty Hartwell" <mhartwe at gmail.com>
> To: "Ten Tec list" <tentec at 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
>> 
>> _______________________________________________
>> TenTec mailing list
>> TenTec at contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>> 
> 
> 
> 
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec