T 50 Vertical
Working Principles


The T-50 vertical has the best DX-efficiency if mounted directly on the ground. Mounting on a flat roof is also efficient , if the guys can be accommodated.

The antenna is attached to its base with U-bolts. The base can be a 2-inch (50 mm) metal tube, 4 x 4 inch (10 x 10 cm) wood pole, etc.

For safety reasons we recommend that the antenna base be between 6 ft. (2 m) and 12 ft (4m) in height.

The antenna is guyed by 3-4 guys (part of kit), attached at about 3/4 antenna height. A second set of guys (also part of kit) may be used at about 1/3 antenna height.

Electrical Principles

The antenna is fed by a 50-ohm coaxial cable of any length and by a 1:4 transformer. For further information, see our T-25 brochure, under "Principles."

Note that the resulting 200-ohm feedpoint impedance guarantees a low loss.

The T-50 can be used from about 1.2 MHz up to 30 MHz continuously and even higher, using a terminal resistor (see T-25 information).

The antenna performs as a "long wire" above 12.5 MHz. The radiation pattern becomes deformed and resembles the wing of a butterfly. Your individual mounting location may, however, compensate somewhat for this effect. Therefore, the gain from 5 degrees to 15 degrees radiation may be zero dB/D or higher.

The T-50 still has significant gain in other directions. The radiation angle is dependent only on its height above ground.

With the antenna mounted at ground level (antenna base less than 1/4 wavelength high), the radiation angle is very low (about 5 degrees).

Since the T-50 is an approximately 5/8 lambda system at 14 MHz, it performs as a surprisingly efficient DX antenna at this frequency.

40 m:

The antenna is a full size 1 lambda radiator. Its gain is close to zero dB/D (plus/minus 1 dB). Note: The "radials" do not act as classical radials. They are a part of a 1 lambda vertical system (radiator 50 ft/15 m + "radials" 15 ft/5 m = 66 ft/20 m = lambda on 40 m).

80/75 m:

The T-50 works as a 1/4 lambda system. Its gain is zero to minus 2 dB/D.

160 m:

On the 160 m band, due to the relationship between the radiator length and wavelength, antenna gain will be less than zero. Using the T-50 as a broadband system with the terminal resistor, gain on the 160 m band will typically range from minus 6 to minus 8 dB/D.

Note: The antenna can be used selectively at 40, 80 and 160 m, using a special tuning transformer. In this configuration, the tuning line and an L/C system in your shack (e.g. matchbox) "tune" the whole system. The advantage is a lower band noise level and slightly higher gain on 80 and 160 m (about 1 dB). Take into account, however, that you then lose the advantage of simple and easy operation on all frequencies. Please contact us for further information.

Sommer Antennas

P.O. Box 710
Geneva, FL 32732
Phone:( 407) 349-9114 | Fax: (407) 349-2485