1. http://www.scrbg.org/

2. The GB3SC# Microwave Beacons What we have (now) FrequencyCallsign Output EIRP Notes 2320.905MHzGB3SCS 3 Watts 3400.905MHzGB3SCF 6 Watts GPS Locked, RTTY Data 5760.905MHzGB3SCC 10 Watts 10368.905MHzGB3SCX 18 Watts GPS Locked, RTTY Data 24048.905 MHz GB3SCK 5 watts Started on 24192.905 47088.905 MHz G8BKE/P200mW Directional, Turned on when needed 70.031G4JNT/P500mW SlowCW Telemetry 2.4 GHz --- <= 100mW 802.11b WLAN Link

3. Had been operational on the Purbecks Had been operational on the Purbecks Good site for GB3SCX and we just about had 3.4GHz running QRP Good site for GB3SCX and we just about had 3.4GHz running QRP Starting to install others. Starting to install others. Kicked off site by mobile phone operators Kicked off site by mobile phone operators So, we needed a new site………….. So, we needed a new site………….. GB3SCX G0API South Coast Beacon Complex

4. Bell Hill Used for contesting by FRARS for years Used for contesting by FRARS for years Unused Versatower and cabin – it had mains power Unused Versatower and cabin – it had mains power Rusty fittings, but all in a useable condition Rusty fittings, but all in a useable condition So we took over the site in 2001 – So we took over the site in 2001 – Loc IO80UU59

5. Good take off in most directions

6. Hut Preparation Had been an animal shelter Had been an animal shelter Need to prevent condensation Need to prevent condensation Limit temperature extremes Limit temperature extremes Walls and door covered in polystyrene Walls and door covered in polystyrene All holes and gaps blocked All holes and gaps blocked

7. Temperature Plots

9. Mast Renovation Needed a lot of work Needed a lot of work Four sets of Guys and stakes Four sets of Guys and stakes New Haul and luffing ropes. New Haul and luffing ropes. Old haul rope broke when winching down Old haul rope broke when winching down New one had to be installed in-situ New one had to be installed in-situ Everthing stripped down and soaked in diesel Everthing stripped down and soaked in diesel Anti-rust paint Anti-rust paint Old PMR Antenna jammed in winch mechanism

10. Cable Support Five 12 metre runs of LDF4-50 plus lightning + spare. Five 12 metre runs of LDF4-50 plus lightning + spare. Too heavy to self hang from top Too heavy to self hang from top Mid point cable support – ‘revolver breech’ supported from pulley Mid point cable support – ‘revolver breech’ supported from pulley

11. Cable hoops prevent swinging Cable hoops prevent swinging Cables can’t be bound together or harness could never be moved ! Cables can’t be bound together or harness could never be moved ! Duct at lower end into hut Duct at lower end into hut

12. DON’T DO THIS AT HOME !

13. The Head assembly Need to survive high winds Need to survive high winds Mounted on scaffold across tower faces Mounted on scaffold across tower faces

15. Antenna Range Tests All antennas mounted close together All antennas mounted close together Tests needed to see if there were interactions / gaps in coverage Tests needed to see if there were interactions / gaps in coverage Antenna test range from G0API driveway to a neighbour across the road – just in far field but with no Fresnel zones Antenna test range from G0API driveway to a neighbour across the road – just in far field but with no Fresnel zones Showed we had a workable system Showed we had a workable system But……. But…….

16. `

17. Tests and Measurements Alford slots weren’t doing their job properly Alford slots weren’t doing their job properly Field distribution along the slot was wrong Field distribution along the slot was wrong Needed small diameter Needed small diameter One coax was much lossier than expected One coax was much lossier than expected Fault in coax connector - ¼ wavelength suckout at 12GHz (for 24GHz, GB3SCK) Fault in coax connector - ¼ wavelength suckout at 12GHz (for 24GHz, GB3SCK)

18. Power Supplies Mains cable 1km long, 1.5mm 2 armoured Mains cable 1km long, 1.5mm 2 armoured 23 ohms loop resistance 23 ohms loop resistance 750 Watts absolute maximum (2.5kW Kettle = Zo) 750 Watts absolute maximum (2.5kW Kettle = Zo) 260 W for beacons and PC = 190 to 210V input. Switch Mode PSU essential 260 W for beacons and PC = 190 to 210V input. Switch Mode PSU essential All beacons run from 12V battery floated across PSU - 10 Amps total All beacons run from 12V battery floated across PSU - 10 Amps total PC has its own UPS PC has its own UPS

19. Mains Failure Extended mains or PSU failure could flatten battery – one 24Ah battery lost already Extended mains or PSU failure could flatten battery – one 24Ah battery lost already Two levels of protection added Two levels of protection added Software puts beacons to standby immediately if mains goes off or DC drops below charge voltage Software puts beacons to standby immediately if mains goes off or DC drops below charge voltage 3A to keep oscillators, ovens and TLM active, 8 to 10 hours 3A to keep oscillators, ovens and TLM active, 8 to 10 hours Then a hardware shut-off if DC drops below 10V Then a hardware shut-off if DC drops below 10V Small auxilliary PSU for TCmd/TLM, cross- strapped, allows for failure of sensing unit / main PSU. Small auxilliary PSU for TCmd/TLM, cross- strapped, allows for failure of sensing unit / main PSU.

21. Earthing / Protection Problems with lightning on an exposed hilltop Problems with lightning on an exposed hilltop Tower metalwork has poor bonding – dedicated conductor up mast for high E-fields Tower metalwork has poor bonding – dedicated conductor up mast for high E-fields Nearby ground strikes are the biggest problem Nearby ground strikes are the biggest problem All metalwork in hut, rack mount, firmly bonded to feeders, mains cable sheath and extensive array of ground radials / rods in 10m circle around the cabin All metalwork in hut, rack mount, firmly bonded to feeders, mains cable sheath and extensive array of ground radials / rods in 10m circle around the cabin Everything jumps together Everything jumps together Varistors were fitted on the mains input after a nearby strike took out the PSU last June Varistors were fitted on the mains input after a nearby strike took out the PSU last June

23. Remote Control Distant site – no quick access for the nominated keepers (30 – 80km trip) – one local op. G7RMG Distant site – no quick access for the nominated keepers (30 – 80km trip) – one local op. G7RMG Radio controlled link, Radio controlled link, Bi-directional, 70cm FM, allows verification of commands. T7F transceiver module Bi-directional, 70cm FM, allows verification of commands. T7F transceiver module PIC Based controller with own battery back up. DTMF tones for control from handie-talkie using rolling set of 5- digit access codes for security. PIC Based controller with own battery back up. DTMF tones for control from handie-talkie using rolling set of 5- digit access codes for security. Three PIN tables for different users Three PIN tables for different users Position in code table accessible on command Position in code table accessible on command Status of each circuit on/off state can be requested Status of each circuit on/off state can be requested Switches 8 circuits on/off via relays with isolated contacts Switches 8 circuits on/off via relays with isolated contacts

24. Telemetry Dedicated PIC based TLM monitor with A/D converters Dedicated PIC based TLM monitor with A/D converters Mains Voltage / Current, DC Volts, Temperatures, Status Switches Mains Voltage / Current, DC Volts, Temperatures, Status Switches Originally just sent CW when demanded on UHF link. Originally just sent CW when demanded on UHF link. Later, 70MHz low power Tx (G4JNT/P) sending basic parameters as CW / SlowCW Later, 70MHz low power Tx (G4JNT/P) sending basic parameters as CW / SlowCW PC logging data via RS232 link from monitor PC logging data via RS232 link from monitor 18km WLAN link and webserver 18km WLAN link and webserver Possibility for alarms sent to users by text message / Email. Possibility for alarms sent to users by text message / Email. Video link Video link

25. 47GHz turned on (We know what you’re doing, Chris and John !)

26. Frequency Locking ‘Simple GPSDO’ on site, supplying 10MHz with typical 10 -9 accuracy ‘Simple GPSDO’ on site, supplying 10MHz with typical 10 -9 accuracy GB3SCF and GB3SCX locked to this using DDS solution – others to follow GB3SCF and GB3SCX locked to this using DDS solution – others to follow 10368.9050068 MHz (32 bit DDS) 10368.9050068 MHz (32 bit DDS) 3400.90499999985 MHz (48 bit DDS) 3400.90499999985 MHz (48 bit DDS) But only to GPSDO accuracy! But only to GPSDO accuracy!

27. Equipment rack

29. UHF Antenna Mast 25A-Hour Pb/H+ Battery Mains Supply Power Monitor Beacon Head Units GB3SCS GB3SCF GB3SCC GB3SCX GB3SCK 12V 30A PSU Switching Relays UHF Command and Telemetry Module Inside the Beacon Hut GPS Locked 10MHz Reference

31. GB3SCF with frequency locked source

32. Head Unit Block Diagram of GB3SCX (the original version before frequency locking) LDF 450 Feed to Masthead Crystal Oscillator Multiplier Bandpass filter 324MHz 648MHz 1.3GHz2.6GHz 108MHz MHz X3X2 DDK004 Source Module +12V X4 Power Amplifier 10.368GHz Slotted Waveguide Antenna

33. Cable Duct into cabin 47GHz 70MHz Dipole