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The PicATUne ATU is another fine project designed by Peter Rhodes, G3XJP and was originally described
in RadCom, September 2000. I am not going to describe it in detail here suffice to say that it is a remotely operated 'L
Match' automatic ATU with excellent performance and several unique operating features.
I used a comercially
produced PCB that was being sold around the time of publication but the original article described the details for
making your own PCB.
This is the ATU mounted in its plastic protective cover on the back wall of the shed at the bottom of
my garden. The small grey box seen at the lower right of the ATU serves no other purpose than to support the main ATU assembly
within the outer case. The Choke Balun is located on the input side of the ATU and is the black object to the lower left.
In this way the whole RF deck is floating above earth which helps to isolate the aerial system from other parts of the Radio
station.
The Choke Balun consists of 21 turns of RG58 coaxial cable wound around seven ferrite rods. Measurements
with my Spectrum Analyser and Tracking Generator indicated common mode losses of 16dB @ 1.8Mhz rising to 50dB at 30Mhz.
I tested a number of different baluns for this application and this one gave by far the best results across the HF spectrum.
The controller is a very simple affair and is mounted under the operating desk. The visual simplicity
belies the amount of operator/ATU interface available and you are referred to the original article to appreciate its
full capability.
NOTE: The PicATUne ATU can only be used by licenced Radio Amateurs. To perform the initial tuning routines
a constant carrier of a few Watts of RF is required. In addition, the ATU communicates with the Operator using CW (Morse code)
and therefore a basic ability to read CW is necessary.
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