ATU

For portable operations small antenna tuner is necessary, especially if you intend to use a piece of wire instead of beams or dipoles. The only one problem to solve is to decide whether you prefer quarter-wave length wire or half-wave one. Presented Mini  ATU has been assembled by the end of April 2001. 

Mini ATU schematic ( painted on 03.05.2001 )

To determine maximum "wire" output which almost represents lowest SWR I have added very simple matching indicator. I don't think that schematic needs more explanation. Just set SW-1 for maximum noise, and adjust C to obtain peak on glowing LED. Detected signal drives LED direct and up to 5 watts of input power no serial resistor is necessary. If you prefer minimum glow to detect matching point just connect serial capacitor (10 pF) to the TX input. LED should be superbrite type.

Mini ATU inside view.  

You can see coil soldered directly to the rotary switch.

Mini ATU front panel view.

Mini ATU rear panel view.

Good looking twins.

How to tune Mini ATU:

Step 1     -    Cut wire to halfwave, quarterwave, multi wave or random length.

Step 2     -    Hang wire as high as possible. Vertical part of wire gives lower angle of radiation.

Step 3     -    Select wire antenna type on the rear switch.

Step 4     -    Use best achievable grounding or approx. 3x3 m of counterpoise.

Step 5     -    Set L switch to position of maximum noise or best RX signal strength.

Step 6     -    When key is down adjust C for maximum LED glow

Step 7    -     Work stations with no problem :'-))

Never hang a wire near power lines !!!!