1. Earth Moon Earth Communications The challenge to build a very large Antenna By Mike Melum Presented to ASPE June 13, 2013

2. Contents How I got hooked The steps – Design – Procure – The Tower – The Mechanics – Electrical/Electronic

3. MOTIVATION The Moon on a clear night is beautiful to behold Typically about 0.5 degree of arc Average 238,000 miles from Earth The thought of reflecting a signal off the moon is seemingly absurd, not quite as absurd as the thought of ‘going there’ but nevertheless not a normal quest Therein lies the challenge

4. How I got Hooked Ham Radio – since age 14 Amateur Satellites The Ultimate ham radio challenge – EME

5. Hooked EME Attracts all kinds of people from carpenters to Nobel Prize winners (~2-3000 world-wide) Technology “Sport” – Civil, Mechanical, Electrical, Electronic – Astrophysics – Moon dynamics are complicated – Control systems – High Power Amplifiers – Low noise, high sensitivity receivers

6. The Steps Acquire the Dish Design Procure parts, materials, services The mounting structure (Tower) The Mechanics

7. Structural Design Tower Requirements – Strength – Height – Cheap Mechanical concepts Make Drawings Ask everyone!

8. Acquire a Dish

9. Original Dish

10. Modifications

11. Design WINDLOADING AND FOUNDATION CALCULATIONS The following assumptions were used in the calculations: 1. Design windspeed = 50 lbs/sq.ft. (approx. 120 mph) 2. Two legs of the tower face away from maximum wind direction to reduce potential for buckling of the tower. 3. Total weight = 15 to 20,000 pounds 4. Dish area = 700 sq. ft. 5. Overturning moment = 875,000 pounds ? 6. Decision: Design for worst case in parked position 7. Design is with antenna parked (EL = 90; AZ = 150 +/-10) (Historically most winds in excess of 30 mph are from this direction)

12. Alternatives

13. Tower (Pilings)

14. Tower Top

15. Rotating Platform

16. Rotating Platform (Part 2)

17. Elevation Actuator

18. Dish Assembly

19. Lift Frame

20. Crane

21. Mounting the Feed Phase 1

22. Mounting the Feed Phase 2 (First Attempt)

23. Mounting the Feed Phase 2 (Final Solution)

24. Mounting the Feed Phase 2 (First Attempt) (Continued)

25. DIY

26. Operating Console

27. Test Bench