Versatile, Dependable, Stealth and Built to Last.

Portable HF Antenna

1.8-54 MHz

The CHA 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.

The antenna will perform very well with a sloper or an inverted “L” configuration. For a NVIS configuration (40M – 80M) the antenna must be installed horizontally with the ground and elevated between 9’ and 12’ high.

The CHA EMCOMM II do not required any ground-plane but will perform better with one. A ground terminal is available for that purpose.


Specifications:
Frequency: 6M - 160M
Power: 500W SSB or 250W CW
RF Connection: PL-259
VSWR: Subject to configuration
Length: 60’
Weight: 1 Lb.
Mounting Configuration: None

The antenna system consists of:

1 X CHA EMCOMM II matching box
1 X 60’ wire

P/N: CHA EMCOMM II

Stacks Image 15
EMCOMM II equipped with ground terminal & stainless steel connectors

Stacks Image 495



$115.00

THE SHIPPING COST ON THIS PAGE ARE VALID FOR THE UNITED STATES ONLY. CONTACT US TO KNOW THE SHIPPING COST FOR YOUR COUNTRY.



Stacks Image 3594
The performances will vary depending of the antenna installation, elevation and counterpoise length used.



EMCOMM II SWR Graph from 2MHz to 54MHz

60' WIRE
ELEVATION 10'
HORIZONTAL CONFIGURATION
25' of RG-­‐8X (Transmission line subtracted (transposed to load)

The results will vary with coax length and antenna elevation.





NVIS INSTALLATION

Stacks Image 436

SLOPER INSTALLATION

Stacks Image 457
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.

INVERTED "L" INSTALLATION

Stacks Image 466
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.

FAQ


1 - FOR A NVIS ANTENNA INSTALLATION CAN I BURY THE COUNTERPOISE?2 - DO I NEED TO USE COUNTERPOISE(S) WITH THE EMCOMM II?3 - HOW MANY COUNTERPOISES ARE RECOMMENDED TO INSTALL AND HOW LONG?
YES - If the installation is permanent, the counterpoise can be buried in the ground.

YES & NO - The counterpoise(s) will always increase the antenna performances. They'll help to reduce the noise level and they'll increase the db in RX and TX. The EMCOMM II will be usable without them but the coax cable will be used as counterpoise by the antenna system which might create some RFI back into the radio and the shack.

It depends: For a NVIS antenna installation only one counterpoise is needed right under the antenna. A 50' - 55' long insulated wire (18, 20 or 22 gauge) will work great. Now for a sloper, invert "L" and a vertical antenna installation 1 to 4 counterpoises can be installed (one in each direction at 90 degree angle). The greater the number the better the performance. The counterpoises should be about 20' to 40' long which will depend of the available space around the antenna. If no counterpoises can be installed then the coax cable will act as a counterpoise by default and a coax cable of 25' to 50' (or longer) is recommended.



Stacks Image 780

CHAMELEON ANTENNA
1283 COMMERCE ST
SPARKS
NEVADA 89431
USA