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The GB3SC# Microwave BeaconsThe GB3SC# Microwave BeaconsWhat we have (now)What we have (now)
FrequencyFrequency CallsignCallsign Output EIRPOutput EIRP NotesNotes
2320.905MHz2320.905MHz GB3SCSGB3SCS 3 Watts3 Watts
3400.905MHz3400.905MHz GB3SCFGB3SCF 6 Watts6 Watts GPS Locked, RTTY DataGPS Locked, RTTY Data
5760.905MHz5760.905MHz GB3SCCGB3SCC 10 Watts10 Watts
10368.905MHz10368.905MHz GB3SCXGB3SCX 18 Watts18 Watts GPS Locked, RTTY DataGPS Locked, RTTY Data
24048.905 MHz24048.905 MHz GB3SCKGB3SCK 5 watts5 watts Started on 24192.905Started on 24192.905
47088.905 MHz47088.905 MHz G8BKE/PG8BKE/P 200mW200mW Directional, Turned on when Directional, Turned on when neededneeded
70.03170.031 G4JNT/PG4JNT/P 500mW500mW SlowCW TelemetrySlowCW Telemetry
2.4 GHz2.4 GHz ------ <= 100mW<= 100mW 802.11b WLAN Link802.11b WLAN Link
Had been operational on Had been operational on the Purbecksthe Purbecks
Good site for GB3SCX Good site for GB3SCX and we just about had and we just about had 3.4GHz running QRP3.4GHz running QRP
Starting to install others.Starting to install others. Kicked off site by mobile Kicked off site by mobile
phone operatorsphone operators So, we needed a new So, we needed a new
site…………..site…………..
GB3SCXG0API
South Coast Beacon Complex
Bell HillBell Hill
Used for contesting by Used for contesting by FRARS for yearsFRARS for years
Unused Versatower Unused Versatower and cabin – it had and cabin – it had mains powermains power
Rusty fittings, but all in Rusty fittings, but all in a useable conditiona useable condition
So we took over the So we took over the site in 2001 – site in 2001 –
Loc IO80UU59
Good take off in most directions
Hut PreparationHut PreparationHad been an animal Had been an animal
sheltershelterNeed to prevent Need to prevent
condensation condensation Limit temperature Limit temperature
extremesextremesWalls and door covered Walls and door covered
in polystyrenein polystyreneAll holes and gaps All holes and gaps
blockedblocked
Temperature Plots
Mast RenovationMast Renovation Needed a lot of work Needed a lot of work Four sets of Guys and Four sets of Guys and
stakesstakes New Haul and luffing New Haul and luffing
ropes.ropes. Old haul rope broke Old haul rope broke
when winching downwhen winching down New one had to be New one had to be
installed installed in-situin-situ Everthing stripped Everthing stripped
down and soaked in down and soaked in dieseldiesel
Anti-rust paintAnti-rust paint
Old PMR Antenna jammed in winch mechanism
Cable SupportCable Support
Five 12 metre runs of Five 12 metre runs of LDF4-50 plus LDF4-50 plus lightning + spare.lightning + spare.
Too heavy to self Too heavy to self hang from tophang from top
Mid point cable Mid point cable support – ‘revolver support – ‘revolver breech’ supported breech’ supported from pulleyfrom pulley
Cable hoops prevent Cable hoops prevent swingingswinging
Cables can’t be Cables can’t be bound together or bound together or harness could never harness could never be moved !be moved !
Duct at lower end Duct at lower end into hutinto hut
DON’T DO
THIS AT
HOME !
The Head assemblyThe Head assemblyNeed to survive high Need to survive high
windswindsMounted on scaffold Mounted on scaffold
across tower facesacross tower faces
Antenna Range TestsAntenna Range Tests
All antennas mounted close togetherAll antennas mounted close together Tests needed to see if there were Tests needed to see if there were
interactions / gaps in coverageinteractions / gaps in coverage Antenna test range from G0API driveway to Antenna test range from G0API driveway to
a neighbour across the road – just in far field a neighbour across the road – just in far field but with no Fresnel zonesbut with no Fresnel zones
Showed we had a workable systemShowed we had a workable system But…….But…….
`̀
Tests and MeasurementsTests and Measurements
Alford slots weren’t doing their job properlyAlford slots weren’t doing their job properlyField distribution along the slot was wrongField distribution along the slot was wrongNeeded small diameterNeeded small diameter
One coax was much lossier than expectedOne coax was much lossier than expectedFault in coax connector - Fault in coax connector - ¼¼ wavelength wavelength
suckout at 12GHz (for 24GHz, GB3SCK)suckout at 12GHz (for 24GHz, GB3SCK)
Power SuppliesPower Supplies
Mains cable 1km long, 1.5mmMains cable 1km long, 1.5mm2 2 armoured armoured 23 ohms loop resistance23 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 260 W for beacons and PC = 190 to 210V input. Switch Mode PSU essentialinput. Switch Mode PSU essential
All beacons run from 12V battery floated All beacons run from 12V battery floated across PSU - 10 Amps totalacross PSU - 10 Amps total
PC has its own UPSPC has its own UPS
Mains FailureMains Failure Extended mains or PSU failure could flatten Extended mains or PSU failure could flatten
battery – one 24Ah battery lost alreadybattery – one 24Ah battery lost already Two levels of protection addedTwo levels of protection added
Software puts beacons to standby immediately if Software puts beacons to standby immediately if mains goes off or DC drops below charge voltage mains goes off or DC drops below charge voltage
3A to keep oscillators, ovens and TLM active, 8 to 10 hours3A to keep oscillators, ovens and TLM active, 8 to 10 hours
Then a hardware shut-off if DC drops below 10VThen a hardware shut-off if DC drops below 10V
Small auxilliary PSU for TCmd/TLM, cross-Small auxilliary PSU for TCmd/TLM, cross-strapped, allows for failure of sensing unit / main strapped, allows for failure of sensing unit / main PSU.PSU.
Earthing / ProtectionEarthing / Protection Problems with lightning on an exposed hilltopProblems with lightning on an exposed hilltop Tower metalwork has poor bonding – dedicated Tower metalwork has poor bonding – dedicated
conductor up mast for high E-fieldsconductor up mast for high E-fields Nearby ground strikes are the biggest problemNearby ground strikes are the biggest problem All metalwork in hut, rack mount, firmly bonded All metalwork in hut, rack mount, firmly bonded
to feeders, mains cable sheath and extensive to feeders, mains cable sheath and extensive array of ground radials / rods in 10m circle array of ground radials / rods in 10m circle around the cabinaround the cabin
Everything jumps togetherEverything jumps together Varistors were fitted on the mains input after a Varistors were fitted on the mains input after a
nearby strike took out the PSU last Junenearby strike took out the PSU last June
Remote ControlRemote Control Distant site – no quick access for the nominated keepers Distant site – no quick access for the nominated keepers
(30 – 80km trip) – one local op. G7RMG(30 – 80km trip) – one local op. G7RMG Radio controlled link, Radio controlled link, Bi-directional, 70cm FM, allows verification of Bi-directional, 70cm FM, allows verification of
commands. T7F transceiver modulecommands. T7F transceiver module PIC Based controller with own battery back up. DTMF PIC Based controller with own battery back up. DTMF
tones for control from handie-talkie using rolling set of 5-tones for control from handie-talkie using rolling set of 5-digit access codes for security. digit access codes for security.
Three PIN tables for different usersThree PIN tables for different users Position in code table accessible on commandPosition in code table accessible on command Status of each circuit on/off state can be requestedStatus of each circuit on/off state can be requested
Switches 8 circuits on/off via relays with isolated contactsSwitches 8 circuits on/off via relays with isolated contacts
TelemetryTelemetry Dedicated PIC based TLM monitor with A/D convertersDedicated PIC based TLM monitor with A/D converters Mains Voltage / Current, DC Volts, Temperatures, Status Mains Voltage / Current, DC Volts, Temperatures, Status
SwitchesSwitches 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 Later, 70MHz low power Tx (G4JNT/P) sending basic
parameters as CW / SlowCWparameters as CW / SlowCW PC logging data via RS232 link from monitorPC logging data via RS232 link from monitor 18km WLAN link and webserver18km WLAN link and webserver Possibility for alarms sent to users by text message / Possibility for alarms sent to users by text message /
Email.Email. Video linkVideo link
47GHz turned on (We know what
you’re doing, Chris and John !)
Frequency LockingFrequency Locking
‘‘Simple GPSDO’ on site, supplying 10MHz Simple GPSDO’ on site, supplying 10MHz with typical 10with typical 10-9-9 accuracy accuracy
GB3SCF and GB3SCX locked to this GB3SCF and GB3SCX locked to this using DDS solution – others to followusing DDS solution – others to follow
10368.905010368.90500068 MHz (32 bit DDS)68 MHz (32 bit DDS)3400.904993400.904999999985 MHz (48 bit DDS)99985 MHz (48 bit DDS)But only to GPSDO accuracy!But only to GPSDO accuracy!
Equipment rackEquipment rack
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
GB3SCF with frequency locked source
Head Unit
Block Diagram of GB3SCX (the original
version before frequency locking)
LDF 450 Feed to Masthead
Crystal Oscillator Multiplier
Bandpass filter
324MHz 648MHz 1.3GHz 2.6GHz108MHzMHz
X3 X2 X2 X2
DDK004 Source Module+12V
X4
Power Amplifier
10.368GHz
Slotted Waveguide Antenna
Cable Duct into cabin
47GHz
70MHz Dipole
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