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Automatic Z-Match Greg P. Le Sage N6LYU May 2010.

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Presentation on theme: "Automatic Z-Match Greg P. Le Sage N6LYU May 2010."— Presentation transcript:

1 Automatic Z-Match Greg P. Le Sage N6LYU May 2010

2 Outline What is a Z-Match? How does it compare to other tuners? Why automate? What's next? Demonstration

3 Harvey Wells Z-Match QST 1955 Reputation for very broad matching range Best for open-wire feedlines No balun Only 2 knobs No variable inductor

4 Original circuit used two coils Similar to L-Network Parallel LC tuned near resonance

5 Single coil version Extensive theoretical and experimental work over the years Very elegant circuit I skipped the series inductor

6 No automatic Z-match found Typical autotuner is an L-network with discrete components Opportunity to do something new Recycled my robot

7 Started with basic manual circuit Z-match is good candidate for automation: 2 knobs Followed on-line prescription for coil Used receiver type variable capacitors Test load is a 1k resistor

8 An ADC Senses Vr Tried to implement VSWR calculation Amplified microstrip signals Large frequency variation Adjacent channels bleed over

9 Control of capacitors Stepper motors were a challenge Tried optical encoding Settled on standard version Backlash

10 Many control inputs Using Parallax Board of Education Added daughter board for many input channels

11 RF shielding was required Application of TX level output sent computer and LCD into convulsions Even at low power, frequency near processor clock (20 MHz and harmonics) is still a problem

12 Capacitor Arcing Experience was that rcvr caps are fine Tuning circuit is a resonator Arcing occurs on 80m Changing feedline length will hopefully avoid this problem

13 Parallax Basic Stamp Stepper motors Variable Capacitors Air wound coil Microstrip coupler

14 Added user configuration Select band: sets series capacitor Sweep through parallel capacitor values

15 What's Next? Use toroid instead of air coil – compact Discrete capacitors Sense frequency Remote to feedpoint – use coaxial line

16 Many examples on-line Most toroid Z-match units used for QRP No automatic versions found

17 N6LYU Automatic Z-Match Read details here: Source code, images, etc. Featured on The DXZone match-antenna-tuner.html Featured on hAntennaTuner/tabid/835/Default.aspx

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