By: KA5WNX
The T-Antenna
Making Low Band Wire Antennas Practical
One of the reasons I really like the T antenna is that it is a static top hat design.
This allows the capacitance to be extremely high on the horizontal and very low on the vertical.
This allows for a very low 50 to 52 OHM feed point at the coaxial cable input.
A gain of 3 to 6 DB can actually be realized as the more wires you have on the antenna, the greater the bandwidth, and the actual gain of the antenna.
This allows the capacitance to be extremely high on the horizontal and very low on the vertical.
This allows for a very low 50 to 52 OHM feed point at the coaxial cable input.
A gain of 3 to 6 DB can actually be realized as the more wires you have on the antenna, the greater the bandwidth, and the actual gain of the antenna.
You see, these top hat static design is actually more omnidirectional than one would think. You see the top hat builds up such a resistance that almost. no signal comes from the top hat. Thus, all the energy is then radiated from the vertical element.
Each leg of the top hat design is 1/4 of one wavelength long. Thus, in the second picture, where you see three bird cages, it is actually eight wires. This makes the design appear as the letter T, and thus the name T antenna.
If you remember in some of the older movies where they had the ship, like the Titanic, you noticed an antenna length the of the entire ship. It is just like the top illustration. This was a tea antenna on all those old ocean liners you saw in the old movies.
The more wires in the antenna, the broader. the bandwidth you can create. Wire 1 would be the lowest frequency used, and the last one would be the highest frequency used. Best of all you can obtain a gain up to a maximum of 6DB over isotropic source. That is awesome for 80 and 40 meters.
Yes, you can create a Inverted V T-Antenna!
Yes, you can create an inverted V style T antenna so that you do not have to have a tall tower, or tall pole for each of the elements of the antenna.
By doing so, you will suddenly realize you can actually contact people locally as there is an extremely low RF lobe with this design.
Also with a sloped in V style T antenna. you will realize an extremely high lobe as well which is advantageous for DXing during favorable Ionosphere conditions.
Each leg of the top hat design is 1/4 of one wavelength long. Thus, in the second picture, where you see three bird cages, it is actually eight wires. This makes the design appear as the letter T, and thus the name T antenna.
If you remember in some of the older movies where they had the ship, like the Titanic, you noticed an antenna length the of the entire ship. It is just like the top illustration. This was a tea antenna on all those old ocean liners you saw in the old movies.
The more wires in the antenna, the broader. the bandwidth you can create. Wire 1 would be the lowest frequency used, and the last one would be the highest frequency used. Best of all you can obtain a gain up to a maximum of 6DB over isotropic source. That is awesome for 80 and 40 meters.
Yes, you can create a Inverted V T-Antenna!
Yes, you can create an inverted V style T antenna so that you do not have to have a tall tower, or tall pole for each of the elements of the antenna.
By doing so, you will suddenly realize you can actually contact people locally as there is an extremely low RF lobe with this design.
Also with a sloped in V style T antenna. you will realize an extremely high lobe as well which is advantageous for DXing during favorable Ionosphere conditions.
Now an interesting Builder's Note:
For low bands only 1/4 wavelength is practical, but, with higher bands such as 10, 6, 2, and 70cm bands you can actually use 3/4 wavelength design.
You see the T antenna total length of the top element can be either 1/4 or 3/4 wave, and the ground is actually a 8 foot or longer ground rod driven all the way into the ground.
For low bands only 1/4 wavelength is practical, but, with higher bands such as 10, 6, 2, and 70cm bands you can actually use 3/4 wavelength design.
You see the T antenna total length of the top element can be either 1/4 or 3/4 wave, and the ground is actually a 8 foot or longer ground rod driven all the way into the ground.
Formula: 234/Frequency in MHz.
Quarter Wave is: 234/Frequency in MHz for total length of the T top portion of antenna. To get the inches instead of a decimal point, just subtract the feet, and multiply 12 times to get the fraction instead of a decimal point left over.
Quarter Wave is: 234/Frequency in MHz for total length of the T top portion of antenna. To get the inches instead of a decimal point, just subtract the feet, and multiply 12 times to get the fraction instead of a decimal point left over.
3/4 Wave:
The formula for the driven element is 702/frequency in MHz.
Using a ground rod as ground, or a 1/4 wave ground plane element of 234/frequency in MHz for the higher bands will work nicely .
The formula for the driven element is 702/frequency in MHz.
Using a ground rod as ground, or a 1/4 wave ground plane element of 234/frequency in MHz for the higher bands will work nicely .
