plot
10 GHz 'Beaconspot' reports as of Sept 2016



spare
        Main and standby 3cm beacon units



pa
              1W PA and driver module



ant
 3cm Waveguide slot antenna and location



East



south



west



north



Select 'view image' on your browser for larger pictures




3cm beacon keyer:  IK0WRB


1sy year drift
First year drift (3cm)

second year drift
Second year drift (3cm)

 
F-drift/2010-2011.
Third year drift (3cm)



4th year ageing
Fourth year drift (3cm)


fifth year ageing
Fifth year drift (3cm)

last year's error
Sixth year drift (3cm)

GB3CAM    Cambridge microwave beacons
IO92WI          Wyton           Cambridgeshire                                                                                                         
 

3cm:  10368.755 MHz                                1.2cm:   24048.870 MHz

reports always welcome, either direct ( gb3cam[at]earf.co.uk ) or via www.beaconspot.eu                       
                                                                                                                                                                                      


Latest news
25.10.11   We now have a red LED light beacon beamed between Cambridge and Newmarket. See:
http://www.earf.co.uk/light_beacon.htm

19.06.13   An Infra-red beacon has been added along side the red beacon - see link above for details



The first of the two Cambridge microwave beacons came on-air on 11th June 2008. This was the 10 GHz
beacon.  Although Wyton is only some 35m asl, the beacon antennas are 30m above ground level - well
above the local tree cover. There is some obstruction due to other antennas on the same site however.
.
beacon-details



beacon antennas
LHS:  24 GHz multiplier/PA/antenna.                         
RHS:  10 GHz antenna.

These units are mounted on the eastern side of the  tower (the camera is looking SE).

cabling
The antenna's are located about  
15m from the rack.

On 3cm, the transmitter power
is 3W, but this is reduced by loss
in the cable to 0.5W at the
antenna.
 



Current 3cm beacon frequency error history 
  (measured every Thursday against a rubidium standard):
measurement
date
07.07.16 14.07.16
21.07.16 28.07.16
04.08.16
11.08.16
18.08.16
25.08.16 01.09.16
Frequency
error
+54 Hz 
 +43 Hz
+55 Hz 
+62 Hz   +79 Hz
 +47 Hz  +79 Hz  +97 Hz   +42 Hz

measurement
date
08.09.16
15.09.16  22.09.16  29.09.16 06.10.15
13.10.16
20.10.16
27.10.16 05.11.16
Frequency
error
+83 Hz  +87 Hz    +58 Hz             

measurement
date
11.11.16 18.11.16  25.11.16  02.12.16 09.12.16
16.12.16
23.12.16 30.12.16
  06.01.17
Frequency
error
 
 






measurement
date
13.01.17 20.01.17 27.01.17 03.02.17 10.02.17 17.02.17 24.02.17 02.03.17 15.03.17
Frequency
error
 








measurement
date
16.03.17 23.03.17 30.03.17 06.04.17 13.04.17 20.04.17 27.04.17 04.05.17 11.05.17
Frequency
error

 








measurement
date
18.05.17 25.05.17 01.06.17 08.06.17 15.06.17 22.06.17 29.06.17 06.07.17 15.07.17
Frequency
error











current drift





      Frequency drift last year  

sixth year drift


 The reference oscillator used in this beacon is a 25 year old Racal 9420 unit. It operates at 5 MHz.

 There is short term drift in the order of +- 10 Hz, due to the combination of controlled oscillator drift and high loop
 time-constant, and as can be seen from these graphs, a long term stability of about +- 75 Hz, due to drift in the
 5 MHz reference.
 
There appears also to be a 30 Hz(ish) jump in frequency from time to time - this can be seen in the graph of weekly   frequency measurements. This is believed to be due to intermittent contact within the rather poor quality worm-drive
timmer capacitor used in the OCXO.

 Something to think about: A 50 Hz error at 10 GHz equates to a clock that gains or loses 150 milli-seconds per year.

For more 1.2cm details contact:  G4BAO                                                      For more 3cm details see: http://www.earf.co.uk/3cm_proposal1.htm