Publicado por: @ea7pu

Los radioaficionados decimos que si va bien no lo toques 😉

¡¡¡EXACTO!!!

Hola, 

· En el libro de Practical Antenna Handbook - Joseph J. Carr & George W. Hippisley W2RU - Fifth Edition

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· En el capitulo PART III - High-Frequency Building-Block Antennas – page 226/228

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Windom The Windom antenna (Fig. 8.7) has been popular since the 1920s. Although Loren Windom is credited with the design, there were actually multiple contributors. Coworkers at the University of Illinois with Windom who should be cocredited were John Byrne, E. F. Brooke, and W. L. Everett. The designation of Windom as the inventor was probably due to the publication of the idea (credited to Windom) in the July 1926 issue of QST magazine. Additional (later) contributions were rendered by G2BI and GM1IAA.

The Windom is a roughly half-wavelength antenna that will also work on even harmonics of the fundamental frequency. Like the off-center-fed dipole, the basic premise is that a dipole’s feedpoint resistance varies from about 50 Ω at the center to about 5000 Ω at either end, depending upon the location of the feedpoint.

In the Windom antenna of Fig. 8.7A, the feedpoint is placed about one-third the way from one end, presumably where the impedance is about 600 Ω. The Windom antenna works “moderately” well—but with some caveats. It is important to again recognize that the return path for a single-conductor feedline is the ground system underneath the antenna and feedline. In distinct contrast to similar horizontal dipoles that are center fed, the extent and quality of the ground beneath the antenna is a major factor in the overall radiation efficiency of the Windom. Further, this is an inherently unbalanced radiating system with all the concomitant issues of “RF in the shack”.

One could just as easily view the Windom as a lopsided “T” antenna or as an inverted-L with a secondary section of top loading attached; in either of those cases, the feedline itself is the primary radiator. The choice of tuning unit for the Windom will depend on the frequencies it is to be used on, but, as mentioned earlier, it is likely that a very good tuner capable of remov-ing large amounts of reactance will be required for at least some of the HF amateur bands available nowadays. An alternative to the single-conductor feedline Windom is shown in Fig. 8.7B. In this antenna a 4:1 balun transformer is placed at the feedpoint, and this in turn is connected to 75-Ω coaxial transmission line to the transmitter. A transmatch, or similar antenna tuner, may also be needed, presumably located at the transmitter end of the transmission line.

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- INFORMACION RELACIONADA EN:

· The long history of “Windom” Antennas - M0RZF

· History: From Windom Antenna to Multiband OCFD

· The New Carolina Windom / Len Carlson - K4IWL

· Off Centre Fed Dipole (OCFD) - Windom Antenna

he "Windom Antenna" was described by Loren G. Windom W8GZ. It could be an ideal wire aerial for use in restricted spaces for multi-band operation. It may also be an good candidate for portable work.

It is a wire antenna, similar to a dipole, but unlike a dipole or doublet which is fed at the exact centre, a Windom or Off Centre Fed Dipole, as the name suggests, has the feed point off center. Current versions of the Windom have a balun at the feed point which is fed with coaxial cable. As with all aerials the aerial should be as high as possible. With the feed point at between 20 and 40 feet above ground the typical claimed impedance will be somewhere in the region of 200 Ohms so a 4:1 balun will typically be required. At greater heights, and depending upon the exact position of the feed point, the impedance may be higher and a 5:1 or 6:1 balun might be a better choice although balun losses will be greater.

The point at which a Windom is fed in the original design, which used an open wire to feed the aerial, was 15 percent off-centre. The current designs, which are fed with coaxial cable, are typically fed about 33 percent off centre, so one leg is 67 percent of the total length and the other leg is 33 percent of the overall length of the aerial.

The bands that are covered depends upon the overall length of the aerial:
11 metres long (approx) should cover 20m, 15m and 10m and the WARC bands with a tuner.
21 metres long (approx) should cover 40m, 20m, 15m and the 10m bands and WARC with a tuner.
41 metres long (approx) should cover 80m, 40m, 20m, 15m and 10m and WARC with a tuner.
80 metres long (approx) should cover 160m, 80m, 40m, 20m, 15m and 10m and WARC with a tuner.

Cut the aerial for the lowest band to be used. In imperial measurements using a familiar formula:

The longer leg will be 468 divided by the frequency and multiplied by .67 = length in feet
The shorter leg will be 468 divided by the frequency and multiplied by .33 = length in feet
According to which sources one refers, the formula can also be found as:
62.2% for one side and 37.8% for the other leg. So:
The longer leg will be 468 divided by the frequency and multiplied by .622 = length in feet
The shorter leg will be 468 divided by the frequency and multiplied by .378 = length in feet

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73 Carlos EC1T

Hola

He visto un BALUN HI POWER 4:1 + RF CHOKE 3 Kw HF ANTENNA WINDOM por  IZ8GCE

que puede ser interesante para la antena windonw ¿alguien lo ha probado?

BALUN Hi Power 4:1 + RF CHOKE 3Kw HF

All'interno di un unico box stagno è presente sia il trasformatore d'impedenza (4:1) che

un Balun RF CHOKE (1:1), ideale per antenne windom.  

        Caratteristiche Tecniche 

• BALUN 4:1 (200 Ohm : 50 Ohm) 
• Rapporto di trasformazione: 4:1 
• BALUN RF CHOKE 1:1 (50 Ohm : 50 Ohm)
• Frequenza: 1.8 - 50 MHz 
• Potenza: 3 KW SSB 1.5 KW CW Dig. 
• Toroide: 2X amidon FT 240-43 
• Cavo 4:1: rame grado II 1.8 mm isolamento su tubino di teflon 
• Cavo 1:1: RG142 cavo in Teflon
• SO-239: ptfe dielettrico ottone 
• Box: abs ip68 
• Bulloneria: inox a2 
• Valvola anticondensa con membrana in goretex

Realizzato con staffetta in policarbonato anti UV e uscite sui lati del box.  

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- Asimismo  Alberto EB4HRA , también realiza  BALUN, UNUN, CHOKE, FCT, EFHW, SWL, QRO, QRP, HF, MF, VHF, conmutación, detección de RF, etc.

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- Asimismo  Salva EA3GJO, también realiza  Balun - Ununs - Chokes

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73 Carlos EC1T

Antonio, ya mejor imposible... no me digas. Carlos, gracias por esto que has puesto de interés general, fantástico. 

Ya ví hace tiempo ese choke del italiano. Yo hice uno esta primavera, pero lo hice exacto al de EB4HRA, 12 vueltas de RG-174 y fenomenal, claro.

De todos es conocido tanto el prestigio de EB4HRA, como el de EA3GJO. Ninguna tontería. A ver nuestro colega Antonio, de Punta, qué decisión toma. La Windom corta es tan fenomenal como la larga, dentro de sus bandas, claro. Porque es multibanda (en las suyas). Se le puede poner unos bigotes para otras bandas. Lo que pasa es que Antonio a veces tiene temporales y lo querrá dejar bien seguro (coño, como cualquiera). Si se decide. Un cordial saludo.

la configuracion del Italiano es la buena por excelencia,para alimentar antenas simetricas balun de tension+ choque.un saludo

Hola.

Os paso las medidas de la antena ANTENA WINDOM "TAGRA  DDK-20" - BANDAS HF 10-15-20-40-80mts - balun 1:6

ver imagen  

·Medidas L1 = 28 metros y 24 centímetros (28,24 mts)

 Medidas L2 = 14 metros y 12 centímetros (14,12 mts)

 La medida total de cable es de 42 metros y 36 centímetros (42,36 mts) incluido  las vueltas de color negro (en el balun y los aislantes)

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- Información relacionada en:

· Diferencias entre Windom con balum 1:6 y con 1:4.

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73 Carlos EC1T