The base of the 7.5 m / 25 ft long radiator is mounted on a sturdy flat aluminum plate
and insulated by two UV-protected polycarbonate rings. Mounted parallel to the
radiator is a Teflon® insulated copper wire. Also mounted on the plate are two HF
transformers (feeding and tuning transformers) and the radials.
The entire structure can easily be mounted to a 40-50 mm / 1.5-2" mast using the two
stainless steel U-bolts provided. Should mobile operation or an approaching storm
or other reasons make it necessary to take the antenna down, this can be done
easily by one person. The radiator can be dismantled and removed from the mast
base in a matter of minutes.
The working principle of our new all-band vertical antenna is similar to the rhombic
antennas, terminated long wires, and the T2FD (terminated folded dipole) or W3HH
antenna. These systems, called "wave antennas" (see ARRL Antenna Book, all
editions), have a very wide frequency range and a terminal resistor, which absorbs
the unradiated energy.
It is interesting to note that there is no measurable SWR reading at the antenna.
Unfavorable electrical surroundings result simply in a higher return to the terminal
resistor. (If you want to check your return power, just insert a wattmeter in your
- 40 m and above
- The antenna is fed by a 50-ohm coaxial cable (feeder line) of any length. A coaxial
broadband transformer (T1) produces a 1:4 50:200-ohm match at A, providing a
power radiation efficiency of 85-98% at 7 MHZ and above (40 through 10 m bands).
- 75-80 and 160 m bands
- The 7.5 m / 25 ft radiator is far from full-size on the 75/80 and 160 m bands. When
operating in these frequencies, parts of the non-radiated rf are fed through a
"tuning line" (B-C). The return path goes through tuning transformer T2 to a 50-ohm
coaxial cable connected to a dummy load at C (typically a 50-ohm terminal resistor).
Using this arrangement, the "return loss" on 80 meters is about 30%or about 1.5 dB
(1/4 s-unit). On 160 meters, the "return loss" is about 60% or 4.5 dB (3/4 s-unit). For
additional information on gain, please see the facts on vertical gain at the end of
this page or at the end of the TCS 25 information.
The terminal resistor should be connected directly to the 50-ohm tuning line
and be capable of handling 30% of the average output
power. For example, a 1.5 KW output signal on cw would have an average output of 750 W
and the terminal resistor must be capable of handling 30% of that power, or an
average of 250 W.
- The antenna is ground-independent and can be mounted almost anywhere. If
mounted on the ground, it should be installed at least 2 m / 7 ft high, for safety
reasons (heads!). Other options might be a roof, a balcony, etc.--almost anywhere.
The antenna can also be mounted at any angle, even in a horizontal position (e.g., in
- Suggestion for the technically minded, experiment-loving ham
- Instead of the real 50-ohm resistor, an L/C system (e.g., a matchbox) can be used at
the tuning cable. This can serve as a selective tuning system, achieving increased
efficiency--especially in the 80 m and 160 m bands. See multi-position switch at C.
Some vertical gain antenna information
- A typical vertical antenna with 0 (zero) dB/D gain in space is the Sleeven 1/2-wavelength dipole. Other 0 dB/D gain systems are 1/2-wavelength antennas like the Zepp-Windom-Fuchs and vertical radiators such as Ground Plane-Discone (all in space).
Antennas shorter than 1/2-wavelength (tuned by a loading coil or traps) have much
less gain. Typical: 1/2-length = 1/4 "power gain" plus loss of traps/coils.
Following are some examples:
* 40 m GROUND PLANE 14 ft / 4.3 m HIGH, CENTER LOADED
Its efficiency is 7%; its gain is -12 dB/D (compared to a full-size system without
losses). This means that only 7 W of a 100 W signal will be radiated. 93 W are
wasted in this antenna.
--See Ham Radio Magazine, Sept., 1982, p. 18 ff, by W1GV.
* A full-size 40 m 1/4-wavelength ground plane is 34.6 ft / 10.5 m high; it has 0 dB/D
*160 m GROUND PLANE 33 ft / 10 m HIGH, 12-OHM GROUND
1. top loaded (big capacitor) -10 dB 10%
2. center loaded, 2-ohm coil -19 dB 1.2%
3. base loaded, 2-ohm coil -20 dB 1.0%
- Note: All gains compared to a full-size radiator and 0-ohm ground. With 2. and 3.
only about 1 W of a 100 W signal will be radiated--99 W is wasted.
- --See Ham Radio Magazine, May, 1983, p. 36 ff, by W7DHD.
* A full-size 160 m 1/4-wavelength ground plane is 136 ft / 41 m high! It has 0 dB/D
P.O. Box 710
Geneva, FL 32732
Phone:( 407) 349-9114 | Fax: (407) 349-2485