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Why Tilt ? - The Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna
Raśl,
Why Tilt ? - The Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna http://groups.yahoo.com/group/Shortw...a/message/9085 Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna http://en.wikipedia.org/wiki/T2FD http://www.electronics-tutorials.com...nna-basics.htm http://www.hard-core-dx.com/nordicdx...wire/t2fd.html http://www.hard-core-dx.com/nordicdx.../t2design.html http://www.hard-core-dx.com/nordicdx.../t2fdfeed.html http://www.hard-core-dx.com/nordicdx.../t2fdcomp.html http://www.hard-core-dx.com/nordicdx...re/t2fd_1.html http://www.radiohc.org/Distributions/Dxers/ttfd2.html An Antenna that incorporates these Four Design Elements to achieve Broad Banded performance : 1. Terminated 2. Tilted 3. Folded 4. Dipole Antenna http://www.cebik.com/wire/t2fd.html Starting with #4 the Basic DIPOLE ANTENNA. http://www.radio-electronics.com/inf...ole/dipole.php http://www.ycars.org/EFRA/Module%20C/AntDip.htm The Dipole is generally a Half-Wave Antenna 'cut' for one Specific Frequency; Mounted at a Set Height for that Frequency and Positioned for a general Off-the-Sides Broadcasting and Receiving. Usually the Dipole is mounted Flat some times in an Inverted "V" or Sloping and even Vertical. http://en.wikipedia.org/wiki/Dipole_antenna How High should my Dipole be ? http://www.qsl.net/aa3rl/ant2.html FWIW - The Radiation Resistance of a properly installed Half-Wave Dipole Antenna is 75 Ohms. The FOLDED Dipole #3 is simply a Dipole that is Folded Back Over on Itself making it Double. If one Dipole is a Half-Wave Antenna then it follows that a Double Dipole is a Half-Wave Antenna Times-Two = a Full-Wave Antenna. The Folded {Full-Wave} Dipole generally has better Band Width then the Half-Wave Dipole Antenna. Most often the Fold Dipole is mounted Flat and sometimes Vertical. The directional characteristics of the Folded Dipole Antenna again are Off-the-Sides for Broadcasting and Receiving. FWIW - The Radiation Resistance of a properly installed Folded {Full-Wave} Dipole Antenna is 300 Ohms. http://www.radio-electronics.com/inf...ded_dipole.php http://www.qsl.net/w4sat/fdipole.htm http://www.arcticpeak.com/antennapag...ded_dipole.htm TV type Folded Dipole Antenna http://www.wfu.edu/~matthews/misc/dipole.html TILTED #2 is used to get the T2FD Antenna off the Horizontal where much of the signal is Off-the-Sides and give the Wire Antenna Elements a little Vertical Dimension to make the Antenna Radiate all around equally in all directions. Tilting also varies the Height-above-Ground of the Antenna and thus the relationship of the Wire Antenna Elements to the Ground has no one specific frequency as in the Basic Dipole Antenna. {Ground Reactance ?) RAUL - SO TO ANSWER YOUR QUESTION Titlting helps to make the T2FD Antenna Omni-Directional. TERMINATED #1 is used to match the impedance characteristics of the Folded Dipole Antenna over a much broader Frequency range then the un-terminated Folded Dipole. TWO SHORTWAVE LISTENER (SWL) T2FD ANTENNAS : NOTE - For the Shortwave Listener this T2FD or TTFD Terminated Tilted Folded Dipole (T2FD) Antenna design seems to be preferred. It uses a 4:1 Matching Transformer (Balun) and a 75 Ohm Coax Cable feed-in-line with a 390 Ohm Terminating Resistor. http://www.hard-core-dx.com/nordicdx.../t2design.html Or this Terminated Tilted Folded Dipole Shortwave Listener's (SWL) Antenna that uses a 10:1 Balun with a 50 Ohm Coax Cable feed-in-line with a 470 Ohm Terminating Resistor. T2FD = http://www.johncon.com/john/T2fd/ GROUNDING of the Terminated Tilted Folded Dipole (T2FD) Antenna is not required since it is a form of a Dipole Antenna an in an of itself does not require a Ground to make it a fully functioning Antenna. However your Radio Shack should have a good earthen Ground Connection and through your Radio Shacks equipment the T2FD will have a Ground Path of sorts. To that end ensure that you have a good earthen Ground Connection for your Radio Shack that is Bonded to your House's Electrical System. hope this helps - iane ~ RHF . . .. . |
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Why Tilt ? - The Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna
"Han" wrote in message ups.com... Hello As far as I know , you have to tilt the antenna to get the right reveiving curve/ angle. for distant stations it is good to receive low incoming signals . By tilting this is achieved. I use a 17 meter long T2FD for over 10 years and it is a antenna which not gives a high signal level but a clean signal! I see this as an advantage Greetings Han, the netherlands Tilting the antenna (assuming the average height remains the same) does not alter the takeoff angle (or elevation of the main lobe). Download the demo version of EZNEC and you can see this for yourself. The elevation angle is purely a function of height above ground of the current loop(s). Dale W4OP |
#3
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Horizontal, Vertical and Sloping Dipole Antennas [Was : Why Tilt ? - The Terminated Tilted Folded Dipole (TTFD / T2FD) Antenna]
Dale [W4OP],
Horizontal, Vertical and Sloping Dipole Antennas http://groups.yahoo.com/group/Shortw...a/message/9090 HORIZONTAL DIPOLE ANTENNA : A basic Horizontal 1/2 WL Dipole Antenna that is Flat with the Center mounted at 1/4 WL above-the-ground and existing in a plane parallel to the ground; can be said to Radiate mostly Off-the-Sides and not the ends. This Horizontal Dipole Antenna has a predictable Take-Off-Angle. - - - The Surface of the Ground acts as a Reflector causing the majority of the Signal to go Up and Off-the-Sides of the Wire Antenna Element in a Horizontal plane : Making the Horizontal Dipole Antenna mostly a Upwardly Radiating Bi-Directional Antenna. VERTICAL DIPOLE ANTENNA : Conversely a basic Vertical 1/2 WL Dipole Antenna that is Straight-Up-and-Down with the Center mounted at 1/4 WL above-the-ground and existing in a plane perpendicular to the ground; can be said to Radiate Equally-All-Around; but not off the ends. Again this Vertical Dipole Antenna has a predictable Take-Off-Angle. - - - Again the Surface of the Ground acts as a Reflector and the majority of the Signal to go Up and Equally Around (Still Off-the-Sides) the Wire Antenna Element in a Horizontal plane : Making the Vertical Dipole Antenna an Upwardly and Outwardly Radiating Omni-Directional Antenna. 30 DEGREE SLOPING {SLANTED} DIPOLE ANTENNA : So we come to a 30 Degree Sloping Dipole Antenna that is Slanted at an Angle Off-the-Horizontal {Vertical?} with the Center mounted at 1/4 WL above-the-ground. Here the majority of the Signal can be said to Radiate Off-the-Sides but a portion of the Signal will Radiate Equally-All-Around; but still not off the ends. As you point-out the Take-Off-Angle would be closer to the Horizontal [Flat] Dipole Antenna. NOTE - The lower Tip of this Slanted Dipole Antenna is 3/16 WL above the ground and the upper Tip is 5/16 WL above-the-ground and the Vertical Dimension of the 30 Degree Sloping Dipole Antenna is 1/8 WL which makes it effectively a 1/8 WL Vertical Radiator. - - - Again the Surface of the Ground acts as a Reflector and the majority of the Signal will go Up and Off-the-Sides of the Wire Antenna Element in a Horizontal plane; however some of the Signal does radiate in-all-directions in the Horizontal plane : Making the 30 Degree Sloping {Slanted} Dipole Antenna less of a bi-directional Antenna and more of an omni-directional {semi-omni} Antenna. Well that is the way that I 'envision' the Radiation properties of the 30 Degree Sloping Dipole Antenna in my-minds-eye 8;-} T2FD / TTFD ANTENNA : Back to Why "Tilt" the Terminated Tilted Folded Dipole (TTFD / T2FD) Antennas - - - The above rational is my simple understanding of One-of-the-Whys for the 'tilting' of the Terminated Tilted Folded Dipole (TTFD / T2FD) Antennas. To help slightly improve the Omni-Directional characteristics of the basic Dipole Antenna in this more Broad Banded design and application. Oops ! - IIRC - FWIW - I am frequently right . . . except when I am wrong, Wrong. WRONG ! { Please Educate and Enlighten Me - Should I Be :-} very little science coupled with mostly common sense - iane ~ RHF [ Keeping It Simple ad Practical = KISAP :] |
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