Mini Satellite-Antenna Rotator Mk1 - SARCNET

Hardware Mk1b

Hardware Assembly

• The hardest part of the build was precision-marking and drilling the motor mounting holes. We recommend sticking adhesive paper labels to the diecast box, scribing construction lines on them using a digital vernier caliper, center-punching and drilling pilot holes first. A drawing of the motor mounting holes can be found in the motor datasheet here. Check three times - drill once.

• Countersink the motor shaft holes on the inside of the rotator case and slip 5mm o-rings over the motor shaft before assembly for ingress protection.

• Add two flat washers to the AZ motor mounting bolts on the side near the lid to counter the chamfer in the rotator case.

• Install a cable gland on the bottom of the rotator case for the PC/Battery and Sensor cables.

• Install the Motor Drivers to the case using countersunk bolts and stand-offs.

• Install the Arduino Pro Micro against the case wall using two layers of double-sided tape on its flat side.

• Prepare an Extra Heavy Duty Speaker Tripod. Try Altronics C0520A. Remove the speaker bracket if fitted.

• Attach a 6mm shaft-hub to the top of the tripod using a 25mm irrigation-pipe threaded plug, 3mm cheese-head bolts, flat washers, spring washers and nuts. Fix with self-tapping screws to the tripod. Replace the grub screws on the shaft hub with cheese-head bolts or cap screws to obtain additional torque.

• Attach the rotator's AZ motor shaft to the tripod and tighten the hub screws.

• Round the sharp edges of a lift arm made from 500x30x30x3mm aluminium angle.

• Make a counterweight from a 101x51x25mm diecast aluminium box: Altronics H0451, Hammond 1590G or similar. Filled with lead to a total weight of 860g/1.9lb.

• Attach the counterweight to one end of the lift arm with self-tapping metal screws.

• Attach the Arrow antenna to the lift arm using Velcro. This is for quick release of the antenna and hand-held operation, if required.

• Attach a 6mm shaft-hub to the lift arm close to the balance point. Ours was 140mm from the antenna end. A slight front-heavy balance offset will reduce backlash.

• Attach the lift arm to the rotator's EL motor shaft using the 6mm shaft-hub and tighten the hub screws.

• Enclose the sensor in 12mm double-wall heatshrink tube and crimp the front end. Mount the flat side of the sensor against the boom with a velcro strap around the boom. See: Sensor Orientation for details. Keep the sensor away from the VHF/UHF driven elements to avoid RF interference to the sensor. Don't use high power for satellites. Use ferrites on the I2C lines if necessary.