Hilltop rfi monitoring system

oct 2002

Intro
Daily plots
images for last 8 days.
Monthly plots of ism band
Monthly plots of 1325 Mhz band
pictures of system
History
schematics
System modification history for high freq system


Introduction:

        The hilltop rfi monitoring system consists of an omni directional antenna covering 10Mhz to 1400 Mhz and a log periodic antenna that covers 1.7 Ghz to 10 Ghz. The antennas are mounted on the hilltop above the control room and feed a receiver consisting of switches, filters, amplifiers, and a spectrum analyzer (100Khz to 22 Ghz). The system runs 24 hours a day under computer control. There are 19 frequency bands that it steps through covering 10 Mhz to 10 Ghz. At each band a 1 minute peak hold is taken, read back by the computer, and then the setup is switched to the next band.  Each frequency band is sampled once every 19 minutes.
     The data is written to disc and the daily plots are generated at 4 am on the next day. The plots created are:

The current daily plots are:

images by frequency for last 8 days:


Low freq (0 -> 1600 Mhz)
High freq (1600 -> 10000 Mhz)
last 8 days _No bpc (.pdf)
last 8 days _No bpc (.pdf)
last 8 days _ With bpc (.pdf)
last 8 days _ With bpc (.pdf)
   
Notes on the images:


2300-2650 monitoring the ism band

    The ism band (2400-2500Mhz) is used by a number of unregulated devices. The lower edge of this band is adjacent to the band used by the 2380 Mhz sband transmit/receive system.
    Plots have been made from the hilltop monitoring system showing the daily usage of 2350-2650 Mhz. The parameters are:
Monthly plots of ism band from hilltop monitoring system:
Year
jan
feb
mar
apr
may
jun
jul
aug
sep
oct
nov
dec
2017
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2016
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2015
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2014
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2013
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2012
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf
2011
.ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf .ps  .pdf

Notes 2017:
Notes 2015:

Notes 2011:
processing: x101/111012/ismrfi_hilltop.pro

Monitoring the 1325 band by month

    The 1325 Mhz band covers 1200 to 1450 Mhz. It contains most of the lband radars.
Monthly plots are done to monitor the status of the band. The monthly processing is:

monthly dynamic spectra,.average spectra  from hilltop monitor 1325 Mhz band
year
jan
feb
mar
apr
may
jun
jul
aug
sep
oct
nov
dec
2017 imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc 
2016 imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc 
2015 imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc 
2014 imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc  imgAll  imgPS  avgspc 


processing: x101/rfi/hilltop/mk1325month.pro

Pictures of system



History



schematics

Schematic of electronics inside huffman box (amps, filters, switches) (.pdf)

diagram of high frequency mast (.pdf)


System modification history for the 1 - 10 Ghz receiver:

    The figure below shows the layout for the 1 to 10 Ghz receiver. A, B, and C are amplifiers. They have been installed, removed, changed, etc.. over time.

Notes:

  • Noise floor 2.2 Ghz is the daily average connector to the full receiver.
  • The cable is 50 feet of low loss heliax. 3.2 db loss at 2 Ghz to 8db at 10Ghz.
  • Since apr02 there have been harmonics of the 1950 cellular phone band. At 3900 Mhz the level was -25 dbm in oct, -33 dbm in june, and not there before 29apr02  (with a noise floor of -58 dbm).

  •  
    Log of changes to high freq receiver
    date ampA ampB ampC R1
    db
    R2
    db
    Noise
    Floor
    2.2Ghz
    Noise
    Flr
    3.5Ghz
    Notes
    04nov12







    hi freq system was off 20oct12-04nov12. ant,ampa brought down to lab after lightning strike.Found broken cable inside box with amp A. replaced cable, installed.
    Started running high freq with 10db attn out for all freq above 2200. Doesn't make a difference in the noise floor. Should think about putting it back in
    17jan08







    system reinstalled on hilltop. monitoring restarted.
    15may07







    spectrum analyzer brought down for maintenance during painting shutdown.
    10jan06






    New ac in rfi shack. Old one was failing.
    19sep05 replaces replaced
    replaced


    noise floor looks ok, but signals absent.
    26aug05 blew blew
    blew


    general power outage,lightning
    29oct02               Found that 50 ft cable connector at box had come 
    loose (the shield). Tightened it up.
    23oct02 g=25db g=25db 0 3 0 -58 -60 didn't change by 20 db..
    22oct02 g=25db g=dbdb g=30db 3 10 -44 -45 added swept elbows box to specAnalyzer
    added R1 
    replaced short cable R1 to input of box.
    9sep02 g=25db
    1.7Nf
    g=25db
    1.7Nf
    g=30db
    2.8Nf
    0 10 -41 -42 back on the air, system saturates 
    with 1.9Ghz birdie
    22aug02            
    amps blown, off the air
    01aug02       0   -50 -42  
    16may02       0   -50 -48 back on the air, not sure which amps were installed
    29apr02       0   -58 -57 blew out 30apr02
    25feb02       0   -55 -57  
    24sep01       0   -55 -56  


    Noise floor:

    On 28oct02 we measured the noise floor of the spectrum analyzer using peak hold. The noise floor is a function of the input antenuation, resolution bandwidth, and the reference level. For the measurement we had the 10db attenuator in. The resolution bandwidth and the reference level used is in the table.

    We then measured the noise floor with the high frequency antenna, ampA, and the 50 foot cable plugged into the spectrum analyzer (the 10db pad was always in) to see how much more gain we needed to get above the spectrum analyz noise floor.  Finally we plugged in the whole high freq receiver (ampA,cable,3db pad, ampB(25db) and recorded the noise floor. The spectrum analyzer steps bands near 6500 Mhz.
    Noise floor measurements 29oct02
    freq (Mhz) ref
    Level
    dbm
    rbw
    Mhz
    spectrum
    analyzer 
    floor(dbm)
    antenna
    ampA,cable
    floor(dbm)
    antenna
    full rcvr
    floor(dbm)
          low freq    
    100 0 .1 -78
     
    500 0 .1 -76
     
    1000 0 .1 -75
     
    1300 0 .1 -75
     
    1400 -20 .1 -79
     
          hi freq    
    1000 0 3 -63  -63 -64(800Mhz)
    2000 0 3 -62.5 -62 -57
    3000 0 3 -62  -62.5 -60
    4000 0 3 -63  -61 -61
    5000 0 3 -62.5 -62.6 -60
    6000 0 3 -62 -62 -61
    7000 0 3 -58 -58 -58
    8000 0 3 -56 -56.5 -56.2
    9000 0 3 -56  -56 -57
    10000 0 3 -56 -56 -57

    Amp A with the 50 foot cable is not above the spectrum analyzer noise floor.
    Amp A, cable, 3db pad, ampB(25db) is above the noise floor at 2ghz but by 3 ghz the noise floor is being set by the spectrum analyzer. We probably could use 10db more but may then have problems with harmonics.



    Online datataking program

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