1. COLD FRONT END Stephen Muchovej Caltech

2. CONSIDERATIONS RF System Itself Physical Considerations Packaging Mounting

3. RF System Requirements Noise temps of < 50K from 1-18GHz 1% Amp Stability, 1 degree phase stability Polar accuracy: 15 dB isolation Ready in Fall – completely done by Summer 2013

4. RF System Note: amp symbols are reversed.

5. Horn Considerations - Spillover

6. Horn Considerations - Cooling

7. Possible Solution Well-matched optics Low spillover Free Design …only operates over factor of 6 in frequency. Means we have to split the system

8. Telescope Focus Point 2m in front of platform. We can put the two systems side- by-side, and cool all components in a single dewar.

9. Features Better system temp ( <50K across whole band ) Perfect beam matching between two systems. Lateral translation between 2 systems. Need 15cm Vertical Translation between two feeds. Needs to rotate to calibrate smaller dishes.

10. Mount Proposal Replace the mechanism up there with a full, self-contained system that bolts onto the ring platform. Uses tracks for linear (and vertical -- focus) translations with actuators. Uses a gear for rotation Install whole rx system at once Adjust y once on installation

11. Mount Proposal Replace the mechanism up there with a full, self-contained system that bolts onto the ring platform. Allows for rotation and translation

12. Prime Focus Inventory Rx and cryo lines. Temp Controlled (TECA) box with: Bias for amps Temp Stable noise source Temp monitoring RF switch Pre-amp module RF-optical converter Ethernet Switch Ethernet controllable power supply Small computer to control Noise Diode, Bias, and Alignment jig (rotation, x, and z)

13. Timeline Other people involved are Tomi Hovatta (most machining) and Russ Keeney March-Mid May: Component Selection and Costing, Rx Design, and Support Jig Design May 15: Order RF components, Quotes on Machining (that won’t happen here) May-July: Machining (Jig, horns, cryostat), control subsystem development August-September: Rx construction, Mechanical testing of Jig, Rx Testing October: Buffer Month. Nov-Dec: Installation/Commissioning

14. Still to define 1.Communications between small computer and control system 2.Amount of focus shift in pointing the telescope 3. Tolerances for Rx placement -- laterally and rotationally 4. Control of focus mechanism (distortion of dish) 5. Budget.