T2FD Antenna

The T2FD antenna: A great all-around antenna for shortwave reception

The T2FD (Terminated Tilted Folded Dipole) antenna is a little-known antenna that performs excellently for shortwave reception. It is compact in size, provides signal gain, wide frequency coverage, and exceptionally low noise characteristics.

The T2FD is essentially a closed loop design with the element ends folded back and joined by a non-inductive resistor. It can be fed with 300 to 600 ohm twinlead or open line, but coax cable connected to an impedance transformer (balun) is a better choice.

The T2FD has a characteristic 5 or 6 to 1 frequency ratio, which means that it works effectively from its low-end design frequency up to 5 or 6 times that frequency. It has a low SWR (app. 1.5). This makes it a versatile antenna that can be used for a wide range of shortwave bands.

The T2FD is also a good performer in terms of noise rejection. This is because the folded dipole design helps to cancel out common-mode noise.

Design:

A (in meters)= 100/f meters, where f is the frequency of the lowest band of operation in MHz. (USN 1/3 model)

B (in meters)= 3/f meters, although 1.66/f has been used.

R1 = 1.1 to 1.5 times the feedpoint impedance.

The value of the terminating resistor is rather critical. Its value depends on the feedpoint impedance and is normally above it. For instance, if 300 ohm feed line is used (or 75 ohm coax into a 4:­1 balun) a good termination value is 390 ohms. For 600 ohm feed line, a 650 ohm value. If a 450 ohm feed line is in use, the correct resistor would be in the vicinity of 500 ohms. The wider the range of frequencies you want to receive the higher R1 should be.

Example:

For operation from 80m (3.65MHz) upwards:

A = 100/3.65 = 27.4m

B = 3/3.65 = 0.8m 

Balun 1:4

R1 – 330 ohm

To build a T2FD antenna, you will need the following:

• 14 gauge stranded, cold-drawn copper wire (length 2A+2B.)

• 5/8" (minimum) diameter wood dowels or acrylic rod for spreader bars (length B.)

• 4:1 balun

• Terminating resistor

• Coax cable

Tips:

• Make sure that the T2FD antenna is at least 3 meters above ground level.

• Avoid mounting the antenna near metal objects, as this can affect its performance.

• Use high-quality materials when building the antenna. This will ensure that it lasts for many years.

Conclusion:

The T2FD is a great all-around antenna for shortwave reception. It is easy to build, performs well, and is relatively inexpensive. If you are looking for an antenna that can give you excellent reception on a wide range of bands, the T2FD is a great option to consider.