Doppler RADAR tests

 

Radio interference test flight  7PM  5-7-2008


In search of persistent 5-GHz interference to the WCVB-TV Doppler RADAR system
as well as 120 MHz AM for air traffic control and safety communications.
Aircraft AM RFI was from the TV station on the Prudential Tower.
Two different issues.

 

 

 

 


MIT was the first and more obvious point of interest.

 

 

 



The interference source operates in the mid-5 GHz region.

 

 


 

Eurocopter   AS-350B


A bit like calling for a cab... but a lot better.

 

 

 

 


Spectrum analyzer with special 5 GHz antenna on the far end of the coax.
The walkies were actually used for non-aircraft communications.
(OK... ham radio on Waltham and Hopkinton 440 MHz and 900 MHz repeaters).

The ship has two permanent Kenwood TK890 radios that are programmed
for both broadcast remote pickup and ham UHF frequencies.

 

 

 

 

 
Work, work, work, work....
 

 

 

 


Current pilot Michael Young who is excellent !

 

 

 

 

 


Flying west past the AM radio towers in Ashland.

 

 

 

 


Hopkinton Doppler RADAR site that was being interfered with on 5.5 GHz.
We definitely observed pulsed, intermittent RFI coming from the east
but could not confirm if the source was originating in Boston, Hopkinton or in between.

 

 

 

 

 


On to Boston as the pulse interference was coming from the east...
but how far east?

 

 

 

 

 


A special 5 GHz antenna was purchased to take an extra special sniff
at the MIT area.  Some pulses were seen but the sample was inconclusive.
Hopkinton seemed to present more intermittent RFI local to the RADAR tower.

 

 

 

 


What an office window !
 
The radio frequency interference investigation continues but this time more to the west and on the ground.  The FCC and frequency coordinators are also engaged and are awaiting our results.

Click here to download and locally play a 5-minute 
Windows Media video file of the flight  (78MB)


Camera: 8M-pixel SONY consumer still camera in "movie mode"
Editor: Windows Movie Maker (free with Windows XP + Vista)

 

 


Next RFI visits  5-13-2008
Weston Nurseries - Tennessee Gas Pipeline Company area
 


 

 


 


Amplitude

 

 


 

Radar allocation RFI freqs
measured in GHz     5-13-08  9:20AM

5.521050352
5.520548218
5.522431456
5.520799279
5.520043130
5.520297168
5.545584846
5.519920615

Most RFI seems to frequency-hop with
a lower amplitude pulse at slightly lower freqs followed by a very high amplitude pulse
at the freqs above.

Since 2002, the WCVB Doppler RADAR has been licensed to operate from 5.350 to 5.650 GHz at 346 kW TPO pulse-mode.
 

 

Frequency
Most RFI seemed to frequency-hop with a lower amplitude pulse at slightly lower frequencies
followed by a single very high amplitude pulse as above.

Click here for a Windows Media video
that illustrates the frequency hopping.

Display specs are similar to the stills above but with less sensitivity (much stronger signal... 1mV ref)