AT-11 Datasheet, PDF (3/15 Pages) List of Unclassifed Manufacturers – AT-11 Automatic Antenna Tuner

Software Changes: Several months after the AT-11 was released, some users noticed spurious noise
emitting from the chip. These "birdies" could be heard on a receiver at various places across the HF spectrum.
The software was changed to allow the AT-11 to go into sleep mode and extinguish the birdies.
The new software changes some of the operating features. At power on and in Semi mode, if there is no
RF, there is no noticeable difference. If there is RF, the tuner will tune to find a match. Once finished with
tuning and RF is removed, the processor will shut down, go into sleep mode and the birdies are gone.
In the sleep mode, the LEDs are disabled. You will not get the SWR indication when RF is present. The
Cap and Ind Up/Down buttons are also disabled while in sleep mode. Pressing the Tune switch with no RF
applied will wake up the processor (the LEDs will flash once). The LEDs will then indicate SWR when RF is
present and the Up / Down buttons will also function.
If you are in the Auto mode, the processor will not go to sleep because it has to monitor the SWR for 3.0
or higher to make another tune. Pressing both Down switches at the same time forces the processor into sleep
from either, semi or automatic mode.
Building the Kit: Before getting the soldering iron out, go through all of the parts in the kit and
familiarize yourself with each component and its placement. Most of the parts are common, but a few of them
may be new to some builders. There are just over 200 parts and 500 solder connections, so take your time.
Once familiar with the parts, start with the eight T-106 toroids (they are red and just over an inch in
diameter). Take care to not drop them, they will break. Use the number #18 gauge wire provided to wind L1-
8. For consistency, we count one turn when the wire passes through the center of the toroid. L1 and L2 just
loop at the bottom of the toroid (figure 2). L3-L8 are evenly spaced around (figure 3). Use the inductor table
to cut the wire to length (figure 4). Wind each toroid in the same direction as shown. Trim the wire to about
1/2 inch and scrape away the insulation from the end. Don't solder them in until later.
Next, wind T1 with 10 turns (figure 5). It is the small, black toroid and just under 1/2 inch in
diameter. The windings use the smaller #28 gauge wire and are made bifiliar. This means to use two lengths of
wire and wind them at the same time. It doesn’t matter if you twist them or wind them side by side. Connecting
Green 1 and Red 2 together forms the center tap of T1. Be sure to note that the wire on the left side come from
under T1 and the wires on the right side come over the top side of T1. Trim the wire to about 1/2 inch and
scrape away the insulation from the end. Do not install T1 until later.
Note that some of the silk screen may have been drilled away when it was fabricated. Use the parts
placement layout in the back of this manual to assist in locating where parts are installed.
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