Antenna 2 element inverted Vee beam 7MHz (40m)
Many radio amateurs consider a 7MHz directional antenna to be a difficult goal to achieve, requiring a high antenna mast and a large amount of duralumin..
If there is enough space, another solution is offered in the form of "forgotten" 2-elemental inverted Vee beam-u. The classic inverted Vee antenna is known and used by many radio amateurs. Each, whoever made it will probably confirm it, that it is an easy to make and walkable antenna. Adding one element creates a two-element fixed directional antenna.
Video: test 2-element inverted V beam 7MHz (40m)
The antenna can be built by a single person and the price is very low. The video shows the first RX test after completion. The comparison took place in the afternoon. The second antenna is 1/4 vertical on a large sheet metal roof, who walks very well. Hear, that DL / SP / I stations are significantly stronger on the beam, while UA almost unchanged - which causes anterior-posterior antenna ratio. Of course, the different polarization and vertical beam angle of the antennas also make a significant difference. Also note the change in background noise level.
Test v CQ WW SSB contest-e
The antenna also passed a demanding test in the form of a CQ WW SSB contest. With 100W, she helped break through pile-ups on KP2, for example, VP2M, VP5, IN, 6AND, KP4, V2, HK, PJ4 etc.. Laci OM / HA6NL did 17x YV with her one ordinary morning. From the local QTH, it is the most difficult direction completely covered by mountains…
RX comparison 2el. inv.V beam 7MHz a 1/4 vertical antenna
Dimensions 2el. inverted Vee beam antenna at 7MHz
Antenna construction
The antenna can be constructed in two ways: as suspended or carried. In the first case, it is necessary to stretch the supporting cable in the direction of radiation. The carried antenna has the tops of the elements mounted on supports. It is only up to individual possibilities, which method is more appropriate. An important factor is the height above the ground. For me it is 13m, which is probably the minimum.
You can find a description of the 2-element inverted V beam 7MHz antenna in the publication 73 Vertical, Beam and Triangle Antennas (MFJ, 1992). The drawing also inspires how to switch directions, but I haven't tried this option.
Simulation 2 element inverted Vee beam antenna at 7MHz with a peak height of 13m
Calculated course of the PSV antenna
Comparison of radiation patterns of three antennas at 7MHz at the same height: half-wave dipole (red), 2-element inverted V beam 7MHz (blue), moxon antenna (black)
Simulation of 2-element inverted V beam 7MHz in MMANA program shows these results: gain 3.3dBd, F / B ratio 9.8dB and impedance in resonance close to 50ohm. The popular HB9CV has better properties (zisk 4,1dBd a F/B cca.20dB), however, it is feasible?
I implemented the carried 2-element inverted V beam 7MHz using combined dural-glass laminate masts. First, we make a radiator with a central insulator and connection to coaxial cables. We'll attach it to the pole, we raise and anchor the mast. We adjust the ends of the radiator with a thin climbing cable and stretch them to the attachment points so, so that the inverted Vee at the top has an angle of at least 100°. We fix the wire to the director on the second pole, we lift and anchor.
2-element inverted V beam 7MHz after completion
Detail of masts and anchors 2-element inverted V beam 7MHz. In the case of two or more people during construction, it is possible to increase the strength of the system by adding a delimiting 6.22m cable to the tops of the antenna and anchor cords from the tops of the masts in front of and behind the antenna
Setting 2-element inverted V beam 7MHz
The advantage of this relatively small height is also that, that we can tune the antenna directly from the ground, just by releasing the arm of the element. We basically adjust the length of the elements as follows, to maintain their function in the antenna, t.j. the director is shorter by 4,8%. Tuning is not complicated, however, it is a bit laborious. It is a very useful helper antenna analyzer.
Measurement of 2-element inverted V beam antenna at 7100kHz, Z = 46ohm +/- j0ohm
Measurement of 2-element inverted V beam antenna at 7030kHz, Z = 39ohm +/- j0ohm
Measurement of 2-element inverted V beam antenna at 7160kHz, Z = 62ohm +/- j33ohm
Possible improvements 2-element inverted V beam 7MHz
There are several options for improvement. It is convenient to include in the power point Wonderful article 1:1. Probably the best W1JR balun, which can be easily made in domestic conditions in good quality and properties. Another possibility is the already mentioned change of antenna direction by extending the director to the reflector. It is also necessary to add another element and make an even more profitable antenna.
2-element inverted V beam 7MHz made the 7MHz band my favorite. You will not join?
