HF antennas, which is the dream of all the OM and the nightmare of their neighbors. There is no way to save the large size of antennas for high frequencies: if the radio electric wave has a certain length, it is inevitable that the appropriate antenna should have a transceiver, to work best, a length proportional to it, within certain thresholds. That these are, according to the common opinion of the layman, a bit 'too heavy for an antenna, has become a catchphrase that often causes social and ridiculous petty disputes which, for reasons of law, and always end surely, the courts, the same way, because, if the law allows the installation, the installation according to the law prevails, socially, on Paturnie cha produces illegal opposition, the latter is more or less massive. The
HF are also sweat seven shirts to OM with regard to their installation, which is a real commitment of capital and labor.
Now is the time to tell my inner struggle on this topic.
If you opt for the economic wire antennas (whether or windom dipoles or more rows) or vertical, there is no directivity, and then picks up a lot of background noise in the reception, you can not always have high wave propagation in transmission and you need an abundance of linear space on the roofs or the ground surface.
In the absence of appropriate space and height, you can use loop antennas (some real sized rings that do not exceed a few meters in diameter http://www.ciromazzoni.com/Loop% 20Antenna.htm ). These antennas unusual and not very showy, originally used quite extensively by the military undoubtedly work well in situations of poor positioning and space, but they need, according to some circuits are very sensitive and very powerful in the reception and transmission, which costs a lot on market integration circuitali dei ricetrasmettitori di elevata qualità: si sa che i militari non hanno, per definizione, problemi di spesa, un civile privato, invece, solitamente sì.
Se si finisce, quindi, per pensare di installare delle antenne direttive molto performanti, ci si trova, in sostanza, secondo me, di fronte a due opzioni di massima: antenne yagi od antenne cubical quad.
Bisogna subito mettersi l’anima in pace: se non si abita sul grattacielo più alto della città e se non si ha a disposizione il suo terrazzo-tetto di sommità, l’opportuna elevazione di un’antenna yagi per HF costituisce già un bel problema in quanto essa, per essere pienamente operativa, non può stare a meno di complessivi 21 m above the ground, it must be necessarily placed at this height on a pole or on top of a tower. Both of these supports are exponentially more expensive as are high. And if they were self-supporting, their prices could become dizzy, a common portfolio, and if even part of the soil, instead of the roof would require, in addition, a project to be submitted to the municipal building permit.
yagi antennas consist of a series of horizontal rods, parallel to each other, supported in the middle of its length to a single support them orthogonal. To avoid the amateur radio to communicate on multiple frequency bands, the economic burden of buying many antennas yagi on most expensive place to stand, spread across a large area, manufacturers have created these antennas multiband yagi that, as such, are crammed with stems. Obviously, these antennas, having more metal bodies of their sisters monoband, weighing much more than them and therefore should be placed on supports, much more robust. In addition, the stems in the center of the multi-band antennas are so close to each other, the antenna itself, to be occasionally subjected to maintenance can not be mounted on masts with lift trucks (because the stems would end up, going down with shopping cart next to the pylon, to clash disastrously against the latter) but only on a lattice or telescopic (ie autoestensibili), or fixed on pylons (from which, if necessary, to get on and off the antenna with the help of a truck with a crane boom!) on poles or reclining on the side (which are required for this purpose, of powerful systems for winch). The smart inventors
an American manufacturer of quality amateur radio antennas rather high (the Steppe http://www.steppir.com/files/Yagi% 20brochure.pdf ) in order to save the amateur radio high cost of the support pole or trellis to large, have had the bright idea to build yagi with carbon rods in the tube, the center which and within which slide by electric stepper motors, controlled by a remote control unit, the true metal of the antenna rods, reduced to thin strips perforated, which can be symmetrically transcribed and rewound at will to reached in each case, the exact distances to the retransmission allowed on each frequency band. This not only has consistently eased the antenna, but has also allowed us to reduce the number of stems so as to produce, in the middle of it, a large empty space that allows the elevation with the side-mast forklifts. The Italian equivalent of this undertaking is the Ultrabeam ( http://www.ultrabeam.it/ ).
Needless to say, of course these particular antennas are quite expensive, though much less of a truss suitable for their equivalent to fixed stems. Then, with a ceiling of at least twelve meters above the ground and a piece of traliccetto of nine meters, the game would be done!
However, there are manufacturers, such as the German Titanex, which were aimed at antenna systems mixed the price lower than the yield remarkable that, in my opinion, it draws: cubical quad multiband antennas with two elements for a dipole spin bands from 40 to 160 m lambda.
HF are also sweat seven shirts to OM with regard to their installation, which is a real commitment of capital and labor.
Now is the time to tell my inner struggle on this topic.
If you opt for the economic wire antennas (whether or windom dipoles or more rows) or vertical, there is no directivity, and then picks up a lot of background noise in the reception, you can not always have high wave propagation in transmission and you need an abundance of linear space on the roofs or the ground surface.
In the absence of appropriate space and height, you can use loop antennas (some real sized rings that do not exceed a few meters in diameter http://www.ciromazzoni.com/Loop% 20Antenna.htm ). These antennas unusual and not very showy, originally used quite extensively by the military undoubtedly work well in situations of poor positioning and space, but they need, according to some circuits are very sensitive and very powerful in the reception and transmission, which costs a lot on market integration circuitali dei ricetrasmettitori di elevata qualità: si sa che i militari non hanno, per definizione, problemi di spesa, un civile privato, invece, solitamente sì.
Se si finisce, quindi, per pensare di installare delle antenne direttive molto performanti, ci si trova, in sostanza, secondo me, di fronte a due opzioni di massima: antenne yagi od antenne cubical quad.
Bisogna subito mettersi l’anima in pace: se non si abita sul grattacielo più alto della città e se non si ha a disposizione il suo terrazzo-tetto di sommità, l’opportuna elevazione di un’antenna yagi per HF costituisce già un bel problema in quanto essa, per essere pienamente operativa, non può stare a meno di complessivi 21 m above the ground, it must be necessarily placed at this height on a pole or on top of a tower. Both of these supports are exponentially more expensive as are high. And if they were self-supporting, their prices could become dizzy, a common portfolio, and if even part of the soil, instead of the roof would require, in addition, a project to be submitted to the municipal building permit.
yagi antennas consist of a series of horizontal rods, parallel to each other, supported in the middle of its length to a single support them orthogonal. To avoid the amateur radio to communicate on multiple frequency bands, the economic burden of buying many antennas yagi on most expensive place to stand, spread across a large area, manufacturers have created these antennas multiband yagi that, as such, are crammed with stems. Obviously, these antennas, having more metal bodies of their sisters monoband, weighing much more than them and therefore should be placed on supports, much more robust. In addition, the stems in the center of the multi-band antennas are so close to each other, the antenna itself, to be occasionally subjected to maintenance can not be mounted on masts with lift trucks (because the stems would end up, going down with shopping cart next to the pylon, to clash disastrously against the latter) but only on a lattice or telescopic (ie autoestensibili), or fixed on pylons (from which, if necessary, to get on and off the antenna with the help of a truck with a crane boom!) on poles or reclining on the side (which are required for this purpose, of powerful systems for winch). The smart inventors
an American manufacturer of quality amateur radio antennas rather high (the Steppe http://www.steppir.com/files/Yagi% 20brochure.pdf ) in order to save the amateur radio high cost of the support pole or trellis to large, have had the bright idea to build yagi with carbon rods in the tube, the center which and within which slide by electric stepper motors, controlled by a remote control unit, the true metal of the antenna rods, reduced to thin strips perforated, which can be symmetrically transcribed and rewound at will to reached in each case, the exact distances to the retransmission allowed on each frequency band. This not only has consistently eased the antenna, but has also allowed us to reduce the number of stems so as to produce, in the middle of it, a large empty space that allows the elevation with the side-mast forklifts. The Italian equivalent of this undertaking is the Ultrabeam ( http://www.ultrabeam.it/ ).
Needless to say, of course these particular antennas are quite expensive, though much less of a truss suitable for their equivalent to fixed stems. Then, with a ceiling of at least twelve meters above the ground and a piece of traliccetto of nine meters, the game would be done!
However, there are manufacturers, such as the German Titanex, which were aimed at antenna systems mixed the price lower than the yield remarkable that, in my opinion, it draws: cubical quad multiband antennas with two elements for a dipole spin bands from 40 to 160 m lambda.
( http://www.titanex.de/frames/quads.html )
Naturally, in this case you can not have everything: the cubical quad antenna is very cheap, easily trailerable in height, and I believe in good-forwarding over very long distances, as well as equipped with a reception sensitivity extraordinary, then, already 16-18 m above the ground, his performance is perfect, however, it has a huge area of \u200b\u200bwind exposure and therefore might be subject to tremendous and sometimes partially destructive effects sail. Today, the mechanical structure of this antenna has been improved and enhanced with spring damping of tension exerted by the wind on its cable arranged in a weaving spider, but its wind resistance remains still very high, so the expenditure, which reduces the height of the side support and value of materials, conversely increases substantially from the point of view of structural strength of this support and cushioned brake system of the rotor, which must be of high quality and robustness.
short, calculator in hand, the accounts are long and complicated: support, height, structure, space, weather at the place of installation, durability of the investment, maintenance, mode and place of purchase, to understand what is really convenient, while maintaining a high value for money is a real pain!
Eventually, however, I am convinced that la soluzione più accettabile, nel caso non si voglia ricorrere ad una abbastanza soddisfacente ma inflazionatissima cushcraft a steli corti e dotati di “strani” cappelli capacitivi alle estremità, sia installare una yagi tipo steppir. Spero di non essermi sbagliato: ai colleghi OM più esperti l’ardua valutazione finale.
Naturally, in this case you can not have everything: the cubical quad antenna is very cheap, easily trailerable in height, and I believe in good-forwarding over very long distances, as well as equipped with a reception sensitivity extraordinary, then, already 16-18 m above the ground, his performance is perfect, however, it has a huge area of \u200b\u200bwind exposure and therefore might be subject to tremendous and sometimes partially destructive effects sail. Today, the mechanical structure of this antenna has been improved and enhanced with spring damping of tension exerted by the wind on its cable arranged in a weaving spider, but its wind resistance remains still very high, so the expenditure, which reduces the height of the side support and value of materials, conversely increases substantially from the point of view of structural strength of this support and cushioned brake system of the rotor, which must be of high quality and robustness.
short, calculator in hand, the accounts are long and complicated: support, height, structure, space, weather at the place of installation, durability of the investment, maintenance, mode and place of purchase, to understand what is really convenient, while maintaining a high value for money is a real pain!
Eventually, however, I am convinced that la soluzione più accettabile, nel caso non si voglia ricorrere ad una abbastanza soddisfacente ma inflazionatissima cushcraft a steli corti e dotati di “strani” cappelli capacitivi alle estremità, sia installare una yagi tipo steppir. Spero di non essermi sbagliato: ai colleghi OM più esperti l’ardua valutazione finale.
[Nella foto l’antenna cubical quad di un collega OM].
