This automatic antenna tuner (ATU) has certainly caught the attention of several owners QRP devices, especially the Yaesu FT-817. It is suitable for any KV transceiver with power from 0.1 to 30W. The adaptive cell is of type L, whose capacity and inductance are switched by relays controlled by instructions from the PIC. The dimensions are approx. (w, h, d): 22.5 x 3 x 13 cm and weight 0.5 kg. Consumption at 11 to 14V power supply ranges from 0.3A during tuning and 8mA after tuning.
Z11 works on the basis of its own meter PSV. O hodnote PSV približne informuje na prednom paneli troma LED diódami: PSV<1,5 zelenou, PSV okolo 2 žltou a PSV>3 červenou. Ďalšia červená LED indikuje ladenie, ktoré sa spúšťa pri detekcii PSV>3 alebo pri stlačení tlačidla TUNE. Ladenie trvá menej ako 5 sekúnd.
The switching of inductances and capacities in the L-cell is by means of memory relays, which is advantageous when working without fine-tuning, when the 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 increasing the PSV to a critical value), the tuning process starts again. However, it can also be manual, but it is much slower and often less accurate. It is controlled by lever switches from the front panel.
I was wondering what the Z11 could tune. For the test, I have a short, only 2.5 meter whip, and tried to tune it on individual bands. However, this extremely short antenna could no longer 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 probably also photogenic, because there are a lot of color pictures in the manual. The components are wire leads (no SMD), which is quite unusual. However, during the test, one LED did not light up. A search revealed an unsoldered lead. Wiring is 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. An earth connection to one of the connectors is offered, but a separate earth terminal would definitely do the trick. Power is also connected through the rear panel.
Comparing ATUs is very challenging. Two aspects are particularly important: the tuning quality and the amount of losses in the matching element. I compared the Z11 with Heathkit HFT-9A tuners (T-cell) 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 equaled the other tuners, or exceeded them by a few (1-3) decibels. Even at 21 MHz, the results were balanced, but then it 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, it can only adapt it. That can never be forgotten.
Tony Lymer, GM0DHD