[RFI] Documenting Power Line Noise

[Hare, Ed W1RFI]

Related to the testing Ford is doing, I stayed late last night and drafted some test procedures and information that, although intended to apply to BPL, may be useful in any such measurements.

Comments appreciated:

http://www.arrl.org/~ehare/bpl/measurements.html
http://www.arrl.org/~ehare//aria/ARIA_MANUAL_TESTING.pdf

There are a lot of pitfalls in doing such testing. First, the sensitivity of a spectrum analyzer may be not quite enough to measure the quiet noise floors at many amateur stations.  Second, the type of detector in the measurement instrumentation will affect the measurement a lot.  Third, it is often hard to use a device like a spectrum analyzer to make such measurements because the over-the-air signals can be easily confused with the ambient noise.

I would like to see more amateurs making quantitative measurements at their stations, though, especially if done over time of day and time of year. There is a lot of information, such as spectrum occupancy; maximum, minimum and typical signal levels; the levels of discrete noise sources and the level of the indeterminate noise in the quiet part of the band.

If any of you want to start doing such measurements at your stations -- and learing a lot in the process, contact me at w1rfi at arrl.org. I will get back to you sometime next week, as I am off on another BPL trip.

Ed Hare, W1RFI
ARRL Lab



> -----Original Message-----
> From: rfi-bounces at contesting.com [mailto:rfi-bounces at contesting.com]On
> Behalf Of Ford Peterson
> Sent: Wednesday, August 25, 2004 1:23 PM
> To: rfi at contesting.com
> Subject: Re: [RFI] Documenting Power Line Noise
> 
> 
> Based on recommendations from this reflector, and from Ed 
> Hare, I have a process defined that should give me a good baseline.
> 
> The power line is scheduled to be back on-line on Friday.  So 
> my window of opportunity is somewhat short.  Tonight, 
> Dewey-N0VO is going to come over with his video camera.  We 
> are going to drive around the neighborhood with the camera 
> running and tuning around on the IC706MKIIG in the vehicle.  
> The best antenna I can muster will be a simple non-resonant 
> 8' whip on the car.  Doing a comparable stunt after the first 
> line is active (next week) and the second line (maybe in a 
> month or so) should provide more than ample evidence as to 
> who's line is spewing RF.
> 
> Last night, I used my HP-141T analyzer to document what my 
> main station antenna hears.  I cannot believe how quiet it is 
> right now.  I have to key down just to make certain the 
> antenna is really connected!
> 
> Based on Ed Hare's recommendation, I am using the 8553B 
> plug-in (0.1-11MHz; 10-110MHz)  to listen on the main antenna 
> in each of the ham bands.  Setting the bandwidth to 3KHz, 
> centering the scope somewhere in each of the ham bands, I 
> clicked off two pictures of the scope display at each 
> frequency.  The first picture has a 50 ohm termination on the 
> scope, the second has the antenna.  Unfortunately, the noise 
> floor of the analyzer is only -80dBm to -90dBm, so connecting 
> the antenna does not elevate the noise floor.  This is still 
> good evidence as looking at that same display previously with 
> the power lines active, the displays of power line hash noise 
> is often in excess of -20dBm.  I am going to re-visit this on 
> Thursday with Ray-KE3QY.  He's bringing a portable scope with 
> a GPIB port for printing.  I will put a 20dB pre-amplifier on 
> the antenna (HP-461A; 1KHz to 150MHz) and see if I can 
> elevate my natural noise floor enough to see it on the scope.
> 
> Thanks to everybody for the help.  This could prove very interesting.
> 
> Ford-N0FP
> ford at cmgate.com
> 
> 
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