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Upcoming Events

Wed May 29 @19:00 - 09:00PM
Club Night
Wed May 29 @19:15 -
Thu May 30 @20:00 -
2m net on DA repeater

Loop and Tuner experiment

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Please note that this project is experimental but has been successfully built in the club but may not be without bugs !

Official Building Instructions.
Official Build Document Link
Hex code for PIC chip as written by John G8JAD
loop tuner 1-15-Hex code link

Initial Instructions as provided for club constructors.
For official document click the link above.

Initial checks

BEFORE installing PIC chip check that the 12V and 5V lines are correct and that the 12V and 5V reach the parts of the circuit they are supposed to reach.


1/ Connect stepper motor to controller to check stepper turning correctly.

· Switch Auto /Man Switch to Man
· Press FAST FWD button and check that the stepper motor turns fast fwd
· Press the SLOW FWD button and check that the stepper motor turns slowly fwd
· Press FAST REV button and check that the stepper motor turns fast rew 
· Press SLOW REV button and check that the stepper motor turns slowly rew

Note current in fast fwd and Rew about 315mA and current in slow fwd and rew about 290mA to 320mA moving about.

2/ Check dead band can be setup

How to select and adjust the dead band or where you wish to set highest SWR permitted and thus allow the tuner to stop

· Apply on RF power.
· Auto/Man switch to auto.
· Press fast fwd and slow fwd button's together.
· Auto/Man switch to man
· Press slow rev button and release to light LEDs, to change dead band value. The more LED's on the bigger the dead band. If you go to high continue to press and release the slow rev button and all will clear and you can start again.
· Once the required setting switch Auto/Man switch back to auto.
· Press slow rev button to set value and the LEDs will go out.

3/ Connect dummy load to Ant connector, connect rig to Tx i/p and connect and stepper motor. Make sure you have the loop tune connected round the right way antenna and Tx i/p

· Switch to man 
· Apply some RF FM /AM power about 1 to 10W and check if SWR on led is No. 1 led.
· With dummy load and stepper connected switch to auto and the stepper motor should not turn.
· Check dead-end control to each setting to make sure stepper does not turn.
. Connect an ATU between loop tuner and dummy load and adjust the ATU to make a mismatch and thus create an SWR. The motor should start turning, then tune the ATU to match the load ie 1.1 SWR motor should stop turning.