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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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