Recenzia LDG Electronics Z11 ATU

This automatic antenna tuner (ATU) certainly attracted several owners of QRP devices, separately Yaesu FT-817. It is suitable for any KV transceiver with power from 0,1 do 30W. The adjusting link is of the L type, whose capacity and inductance is switched by relays controlled by instructions from the PIC. The dimensions are approx. (š, in, h): 22,5 x 3 x 13 cm and weight 0,5 kg. Power consumption 11 up to 14V ranges from 0.3A during tuning and 8mA after tuning.

Z11 works on the basis of its own PSV meter. The PSV value is approximately reported on the front panel with three LEDs: PSV<1,5 green, The next step was to check the UHF duplexer 2 yellow and PSV>3 red. Another red LED indicates tuning, which is triggered when PSV is detected>3 or when pressing the TUNE button. Tuning takes less than 5 seconds.

Switching of inductances and capacities in the L-cell is by means of memory relays, which is advantageous when working without fine-tuning, when consumption is almost zero. The maximum inductance is approximately 20uH and the capacity is 2700pF. These two parameters are the criteria for adaptation, especially in the lower bands. The minimum inductance is 0.11uH and the capacity is 10pF. Relays switch them roughly in a row of two, e.g.. 10pF, 20pF, 39pF, 82pF,….

The ATU has no memory or counter, after changing the band (or an increase in PSV to a critical value) the debugging process starts again. However, it can also be manual, however, it is much slower and often less accurate. It is controlled by lever switches from the front panel.

I was interested, what Z11 can tune. I'm short for the exam, only 2,5 meter whip, and tried to tune it on individual bands. However, this extremely short antenna could not be tuned to 7MHz. After extending the vertical to 3 meters, Z11 was already able to adapt it on this band.

The interior design is very clean and apparently photogenic, because there are a lot of color pictures in the manual. The components are wire leads (which we use have this numbering), which is quite unusual. However, during the test, one LED did not light up. The search revealed unsoldered terminals. Connection not difficult, a technically proficient radio amateur can handle the construction by himself (also sold as a kit).

There are two SO-239 connectors on the rear panel. One connects the ATU to the transceiver, the other to the antenna. However, the grounding clamp is missing. It is offered to connect the ground to some connector, but a separate grounding clamp would definitely do the trick. Power is also connected through the rear panel.

Comparing ATUs is very difficult. Two points of view are particularly important: the tuning quality and the amount of losses in the matching element. I compared the Z11 with the Heathkit HFT-9A tuners (T-section) and two L-cells on the W3EDP antenna. The measurement was carried out on an Agilent E4416A power meter using an 8482A probe.

The results of the Z11 were excellent in the lower bands, where it at least matched the other tuners, or even a couple of them (1 – 3) exceeded decibels. Still on 21 MHz, the results were balanced, but then he started to lose significantly (up to 5 dB).

If I have to evaluate the Z11, I have to say, that I like it. It is very pleasant to switch between bands and not worry about anything. Of course, the tuner cannot turn an ineffective antenna into an effective one, just adapt it. That can never be forgotten.

Tony Lymer, GM0DHD