ECO ANTENNE ATX-1080 Antenna HF multibanda trasportabile dai 80m a 2m, per l'FT-817 FT-818, KX3, X5105, G90

ATX-1080

Antenna multiband for transportable QRP equipment for "field-day" operations

Particularly suitable for devices such as the Icom IC-705, Yaesu Ft-817 and FT-818, Xiegu X-5105 and G-90, Elecraft KX2 and KX3

As as many QRP transportable devices such as the yaesu FT-817/FT-818 are supplied, the Xiegu X-5105 or G-90 and the various Elecraft KX2 and KX3, do not include an antenna for operation in the HF band. One of the first products introduced to solve this problem was the Walkabout ATX antenna. The antenna is believed to be a project Mizuho, ??made under license for Waters and Stanton by Sandpiper Antennas in Wales. Since then, alternatives have appeared that promise miracles, but the ATX Walkabout is still the best portable whip antenna for the 817, as well as being the least expensive.

Today we propose it again as ECO ANTENNAS with its original name ATX-1080

Description

The ATX-1080 It is a base loaded whip, a conventional and proven design used in many mobile antennas. The basic loading coil has sockets for the main ones amateur bands, from 80 to 6 m. Resonance is achieved by selecting the appropriate grip (effectively shorting the bottom of the loading coil) and then finely adjusting by extending or reducing the telescopic whisk. It is necessary a ground or counterweight to get a good match and get the better radiant efficiency.

One Downside of the ATX-1080 design is that the WARC bands don't have their own dedicated taps. Instead, they are tuned by selecting the next lower band and reducing the length of the whip. This results in a whip length of approx 40cm on 30m.
The ATX-1080 can also be used on 2 meters. The paper of instructions states that it makes a "reasonable" 5/8 wave on 2m.

The AT-1080 original had a BNC plug for mounting on the front panel socket of 817. However, the BNC on the front panel of the FT-817/FT-818 is not designed to withstand the strain that this antenna may cause.

Subsequently a version with a right-angle PL-259 socket was introduced to fit to the rear antenna socket. This is a mechanically improving solution.

The latest Mark II version of the ATX-1080 has a screw connector by default 3/8" and comes with a set of adapters that allow for conversion into a BNC in-line, PL-259 in-line or PL-259 right angle fitting.

Counterweights

For function effectively and present a good match to the transceiver, the AT-1080 must be used with a counterweight of appropriate length for each band. To facilitate quick configuration, follow the steps below table.

Although nominally correct length for a counterweight be a quarter wavelength, it should be noted that the optimal length of the counterweight depends a lot on the situation of the antenna, on how close it is to the ground and from what other grounding (such as power cables) is present. The effect of the length of the whip on the resonant frequency is also great strong. Therefore you are likely to find that different values work better for you. This also explains the differences between this graph and the following using a tape measure counterweight, which was made at a different time and in a different situation.

Length Band Whip Length [1]
Best SWR
40m See note [2] 9 sections + 2 "1.1:1
20m - 538cm 9 sections +1" 1.6:1
17 m - 444 cm 4 sections + 1 3/4" 1.1:1
15 m - 373 cm 8 sections + 2 1/4" 1.1:1
12 m - 295 cm 6 sections 1.4:1
10m - 241cm 9 sections + 3" 1.3:1
6 m - 120 cm 7 sections + 3" 1.3:1
2 m - no c / p 8 sections 1.2: 1

Notes:

The sections extended are counted from below
The 40m counterweight includes 36ft of cable. About a third of this from the end is rolled (3 inches in diameter) by adding or removing turns until the minimum SWR is reached.
The cable is sheathed in 55/0.1 mm extra flexible PVC
Counterweights should be placed as far away as possible and away from metal objects. The curves and proximity to metal objects will jar them and may not be possible compensate by adjusting the whisk.

Measurements for 30m were not attested due to my feeling that the ATX-1080 would be too inefficient on this band. Measurements for 80 m were not taken for the same reason, other than the fact that a resonant counterweight should have been longer of the thread available at that moment.
A counterweight tape measure