The virtual ground balun presented hereby is the practical application in the field of the short wave radio communications of what the Author has previously created for scientific purposes. It, infact, along with the virtual ground balun for doubling the ½ wavelength folded dipole antenna, descends from the radio-electric circuitry for the suppression of anyone of the two branches of a ½ of wavelength open dipole.

Errante's balun is, essentially, a pure electrical transformer which, in its most elementary layout, has a minimum of 3 tuned circuits: a primary circuit (primary winding LC network) and 2 secondary circuits (secondary windings LC networks).
Generally, the Errante's balun secondary circuits are identical to each other in order to feed symmetrical balanced antennas. When necessary, the secondary windings can be formed to have impedance values different between each other, while maintaining the phase angle difference of the balanced terminations to a constant ±90 degree with respect to the virtual ground node. Moreover, as all the pure electrical transformers, Errante's balun can be made to have more than a couple of secondary windings.

Errante's balun is characterized for NON allowing any impedance transformation to take place unless its terminations impedance values are matched (NON-fluctuating impedance).
Errante's balun terminations impedance values are set by design, hence the impedance transformation ratio is a function of them and not viceversa, unlike it happens with any other balun arrangement. See for example the Guanella's or the Ruthroff's transformers which are instead characterized by having a fluctuating terminations impedance values, as they are nothing else than an arrangement of auto-transformers, their input and output circuits are unseparable and, therefore, any change made to their primary circuits will inevitably affect their secondary circuits.
In practice, a balun having a fluctuating termination impedance value carries out its impedance transformation duty within a very ample range of impedance values, changing its input termination impedance according to the one of its load and viceversa. Therefore, supposed we have a Guanella's type balun with a transformation ratio of 4:1, it will show an input impedance of 75 Ohm if its load impedance is of 300 Ohm, or it will show an input impedance of 50 Ohm if its load impedance is of 200 Ohm. This cannot happen if an Errante's type of balun is employed, because each termination impedance value is a fixed property of the relevant termination and does not vary even if there is a change in the values of the impedance of the circuits (antennas or transmission lines) connected to them.
By limiting the line-load system impedance to the imposed values only, it is possible to inhibit both lines and loads (antennas) from giving origins to unwanted resonances, which are, generally, harmonic resonances, very often deriving from the presence of more than a load on the same feed-point, which generates alternative paths for the RF. (for example: multiple dipoles o monopoles, fan antennas and so on). This is something not to be underestimated, not only with regard to the transmitting phase but and above all, to the receiving phase as well. Employing a NON-fluctuating impedance balun, infact, introduces a very high rejection to interfering radio signals from sources outside the bands of the radio spectrum for which an antenna is ment. This translates in an excellent stability and selectivity of the transmission line or antenna systems which employ Errante's baluns.

A virtual ground balun represents the ideal device for the correct feeding of dipole and loop antennas. The virtual ground balun carries out many functions at once allowing to:
1) match the RF source impedance to the chosen load while introducing neglectable insertion loss of power;
2) transform the RF signal fed to it into two identical portions with the correct phase angle difference for the natural feeding of open or folded dipoles and loop antennas;
3) obtain a virtual ground node for the correct polarization of its unbalanced port;
4) obtain a common ground path for the dissipation of the charges induced by the electrostatic phenomena;
5) obtain an high de-coupling between its two balanced ports.

The generic virtual ground balun's schematic diagram is shown here below.

The virtual ground balun is housed inside a weatherproof rugged metal enclosure having two separate compartments: one hosts the balun circuitry while the other one protects the coaxial connectors. The said metal enclosure not only ensures an high mechanical robustness and a total stability against the weather agents, it also works as the general electric conductor for all the references to the virtual ground node. Such an enclosure ensures also a full electrostatic shielding of the RF balun transformer circuitry.

Radiondistics claims the originality of the balun's unique electromechanical layout, as well as the balun radio-electric circuitry.

 

ERRANTE's BALUN Virtual ground balun for folded dipole & loop antennas A state-of-the-art high power broadband HF balun

Patent n.0001347484 (ITAPA20030019) and Patent n.0001347486 Visit the European Patent Office to see all the patents of mine HERE !

A VIRTUAL GROUND BALUN FOR DOUBLING THE ½ WAVELENGTH FOLDED DIPOLE ANTENNA by Francesco Errante Scientific purposes a. The VIRTUAL GROUND RF BALUN TRANSFORMER described hereby allows the doubling of the ½ wavelength folded dipole's radiator. b. The virtual ground RF balun transformer described hereby allows to demonstrate that in a ½ wavelength folded dipole antenna, its radiator (having a characteristic impedance of 300 ohm) acts as it was made of two distinct radiators, identical to each other and coinciding with each other, while being fed in a counterphase arrangement, having each of them a characteristic impedance of 150 Ohm, referred to the virtual ground node. c. The virtual ground RF balun transformer described hereby allows to demonstrate that the ½ wavelength folded dipole radiator and, indeed, any other resonant loop, be it made of any shape, with both a single turn or a multiple turn winding, when it is correctly fed with a sinusoidal radio-electric signal of a proper wavelength, it is always interested by electric currents that flow along its entire length from one end to the other in a clockwise direction for a semi-period and anti-clockwise during the next semi-period or viceversa. Circuit description The Author, by means of a particular radio-electric circuitry for the suppression of any which one of the two branches of a ½ of wavelength open dipole, has previously demonstrated that it is, indeed, possible to feed each of the two branches of an ½ wavelength open dipole independently, so that they can become electrically independent from each other allowing, therefore, to suppress any which one of them without repercussions on the condition of resonance and radiation of the remaining one. On that occasion, the Author has introduced the reader to the concept and the method for generating a virtual ground node for the separation of the dipole's branch currents. The ½ wavelength folded dipole antenna has a single wiring radiator and, therefore, does not allow the independent usage of the currents flowing on it, both in a clockwise and anti clockwise way. The present invention allows to split up the folded dipole radiator into two nearly-coinciding wirings in order to demonstrate that the single folded dipole radiator acts as if it was made of two identical but distinct wirings coinciding with each other and each working cyclically for the duration of a semi-period. This result has been achieved by means of a lumped-constants radio-electric circuit, based around a broad-band flux-coupled radio electric balun transformer(1) winded on a binocular type ferrite core having a primary winding(2) exhibiting an impedance value equal the one of the transmission line(10) being used and a center-tapped secondary winding(3) exhibiting an impedance value of 150 + 150 Ohm. The said impedance values are referred to the virtual ground node(4 & 6). (a virtual ground node is defined as a point in an electrical circuit that appears to be at ground, but is not actually attached to ground, it is therefore, a node having a 0 degree phase angle difference with respect to ground and has the same electrical potential as the Earth) The virtual ground node is made available to the whole circuit by means of a very short electrical connection(6) between the transformer center-tapping(4) and the balun chassis(5). The transformer's working point is optimized by compensation with the employment of high-voltage RF duty capacitors(9). It is important to highlight the fact that the two independently fed branches(7 & 8) can also be independently rotated around their common axis to give a variable radiation pattern which ranges from a typical dipole's radiation pattern, if the arms are parallel to each other or a quasi-omnidirectional radiation pattern in the case of the arms being placed perpendicularly to each-other (turnstile arrangement). The balun described hereby is characterized by being a NON fluctuating impedance RF electrical transformer. All of its terminations impedance values are set by design, hence the impedance transformation ratio is a function of them and not viceversa, unlike it happens with any other balun arrangement.

Operational advantages:

a. the virtual ground balun allows the feeding of dipole and loop antennas with much less loss than conventional baluns b. the virtual ground balun allows an aerial to exhibit a much larger bandwidth compared to when the same antenna is fed by a conventional balun. c. the virtual ground balun allows an antenna to exhibit a much stronger immunity to parasitic capacitive effects compared to when the same antenna is fed by conventional baluns. d. the virtual ground balun allows an antenna to exhibit a strong resonance stability, regardless of the level and inclination of it above the ground. e. the virtual ground balun allows an antenna to exhibit a much stronger immunity to out-of-band emissions compared to when the same aerial is fed by a conventional balun. f. the virtual ground balun allows an antenna to exhibit a much stronger immunity to electrostatic charges and noises compared to when it is fed by a conventional balun. g. the virtual ground balun, owing to the constructive and destructive interference phenomena taking place in the transformer allows the dipole antenna to exhibit a sharper radiation/reception pattern (off the beam axis signal rejection) compared to the same aerial when fed by a conventional balun. h. the virtual ground balun allows a much faster antenna deployment time compared to conventional baluns. i. the virtual ground balun allows an antenna to exhibit a much better compatibility with highly populated environments (EMC TVI) compared to when it is fed by a conventional baluns.

Applications:

a. SHORT WAVES FIXED & MOBILE RADIO STATION FOR CIVIL & MILITARY PURPOSES   b. STEALTH, FAST & TACTICAL DEPLOYMENT PURPOSES   c. SEARCH & RESCUE SERVICES  d. SHIP to SHIP & SHIP to SHORE MARINE COMMUNICATIONS e. DX-ing and metropolitan HAM RADIO STATIONS f. ELEMENT in ARRAYS of AERIALS g. RADIO-PHYSICS LABORATORIES see also SWR-metered balun