Re: ARLA/CLUSTER: Antena de Emergência para HF com 18,28 metros e montagens NVIS (Bandas de 40M / 80M).

[João Costa > CT1FBF]

Online Manual of Portable HF Antenna CHA EMCOMM II

http://chameleonantenna.com/BASE%20ANTENNA/CHA%20EMCOMM%20II/CHA%20EMCOMM%20II.html

2014-12-29 16:43 GMT+00:00 João Costa > CT1FBF <ct1fbf  gmail.com>:
> Onde se lê:
> For a NVIS configuration (40M / 80M) the antenna must be installed
> horizontally with the ground and elevated between 9″ (22,86 cm) and 12″ (
> 30,48 cm) high
>
> Deve ler-se:
> For a NVIS configuration (40M / 80M) the antenna must be installed
> horizontally with the ground and elevated between 9` (2,74 m) and 12` ( 3.65
> m) high.
>
> João Costa (CT1FBF)
>
>
> 2014-12-29 16:31 GMT+00:00 João Costa > CT1FBF <ct1fbf  gmail.com>:
>>
>> Chameleon EMCOMM II Portable HF Antenna Antenna
>>
>>
>>
>>
>> 1.8-54 MHz. The Chameleon EMCOMM II Antenna has been specially designed
>> for backup emergency HF system or permanent installation. The integral
>> broadband impedance matching network (transformer 5:1) allows broadband
>> antenna tuning. It is the perfect backup antenna for apartments,
>> condominiums, homeowners associations, deed restrictions and CCRs
>> (Covenants, Conditions & Restrictions), ARES, RACES, MARS, EMCOMM, NVIS,
>> First Responders and especially for Emergency Preparedness. The unit is
>> totally waterproof. The antenna is 60’ long and covers 6M to 160M. An
>> external tuner is required.
>>
>>
>> Specifications:
>>
>> ·        Frequency: 6M – 160M
>>
>> ·        Power: 500W SSB or 250W CW
>>
>> ·        RF Connection: PL-259
>>
>> ·        VSWR: Subject to configuration
>>
>> ·        Length: 60’ = 18,28 m
>>
>> ·        Weight: 1 Lb.
>>
>> ·        Mounting Configuration: None
>>
>> The antenna system consists of:
>>
>> 1 X CHA EMCOMM II matching box
>> 1 X 60’ (18,28m) wire
>>
>>
>> The antenna will perform very well with a sloper or an “Inverted-Vee”
>> configuration. For a NVIS configuration (40M / 80M) the antenna must be
>> installed horizontally with the ground and elevated between 9″ (22,86 cm)
>> and 12″ ( 30,48 cm) high.The EMCOMM II does not require a ground-plane but
>> will perform better with one. A ground terminal is available for that
>> purpose. Power capacity is 500 watts SSB or 250 watts CW. SO-239 input.
>>
>> Videos:
>>
>> http://goo.gl/v2UeV6
>>
>> http://goo.gl/BZXi2S
>>
>>
>> NVIS Installation:
>>
>>
>>
>> The sloper is considered the most unusual antenna system and can be
>> difficult to get to work properly. The sloper may exhibit some gain in one
>> direction, but usually has omni direction pattern. There are two types of
>> sloper, the full sloper, really a dipole mounted with one end higher than
>> the other. The half-sloper (EMCOMM II) is fed at one end with a “ground
>> system” or counter poise provided by either physical ground if fed at lower
>> end of sloper. If the sloper is fed at the top, then other factors provide
>> the “ground”. In most cases, a sloper mounted on a tower, then the tower and
>> importantly, the beam mounted on top, act as the counterpoise.One successful
>> version of the sloper (most folks call any kind of sloper simply a “sloper”
>> regardless of its type) is one that is fed with coax. The antenna is fed
>> from the top and installed on a tower with a beam on top. The center
>> conductor of the coax feeds the sloper wire and the shield is carefully
>> bonded to the tower structure. In addition the beam, rotor, and mast are
>> electrically bonded to the tower (here a heavy braided strap connecting the
>> mast to the tower is recommended). The theory is that the sloper is fed at
>> the top and the high current point is high just under the beam, leading away
>> from the tower.
>>
>> The sloper has been reported to be hard to get to work in some cases. When
>> it works, its performance when used with a tower and a beam is very good.
>> Considering the cost of materials (assuming the tower is in place already)
>> the sloper should be considered.
>>
>>
>> This is most likely the least expensive high performance antenna you can
>> erect for 40M, 80M and 160M (limited performance). It is worth investigating
>> since it needs only one high point in the relative clear to be effective
>> (the horizontal far end can be at a lesser elevation, details later).Most
>> likely you will need to use an external antenna tuner.The main radiating
>> component of the “L” is the vertical wire, that’s what makes it a very good
>> groundwave and DX antenna. So it would be good if this can be kept in the
>> clear, or several feet away from your tower, and of course, as high as you
>> can make it. The horizontal part may slope downward, or bent several times
>> to accommodate any obstacles. Keep in mind, the more you bend the element
>> back on itself, the more of the radiated signal is canceled out.Sometimes it
>> is not possible to have the vertical section longer than the horizontal
>> section. This will result in more of the signal being radiated skyward to
>> which NVIS (Near Vertical Incident Skywave) will occur.  NVIS is a
>> propagation method that provides usable signals in the range between ground
>> wave and skywave distances (usually 30 to 400 miles).Before we go any
>> further, this antenna requires a robust ground system. If your ground is
>> poor, the antenna efficiency will be poor, and you will be troubled with RF
>> in the shack.The radiation pattern is omni directional, with a possible
>> minor lobe in the direction of the horizontal portion.
>>
>> Price: $115.00 USD
>>
>> Link
>>
>> Fonte: Sparky\'s World of Amateur Radio
>>
>>
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>