Wednesday, December 31, 2014

"Driveby" App Stationary Test


Today I tested the sensitivity of the "Driveby" app I've been working on the past month or so.  This wasn't a highly technical sensitivity test, but rather just an experiment to demonstrate how the application as a whole functions once it's warmed up, calibrated, and ready to run.  

During this test I used my 50 Mhz 57 foot long boom yagi antenna which is located at the top of a 47 foot high tower.  The feedline is LMR600.  I aimed the antenna at the start of the test due south at 180 degrees which is one of my more quite directions.  Midway through the test I rotated the large yagi 180 degrees from South to due North.  

North of me there is a 49 Mhz Baby Monitor.  So this is a pretty 'real-world' test of what I can expect from the graphing of the data while I'm driving around.

Part of this experiment when I actually do take this all on the road is to map out locations where 49 Mhz Baby Monitors physically located.  (Yes I know that MAY seem creepy to those of you how have never operated on the 50 Mhz ham band you wouldn't understand).  So the reason behind attempting to locate these baby monitors as part of this project is that there are all sorts of noise sources.  Band pass filters in radio's and after the radio can really only do so much, and in fact they're not really effective at all in eliminating noise from the 49Mhz range.  Most baby monitors is really quite broad, and can be really lousy RF neighbors.

So the reason for attempting to locate these monitors is so that I can later send the residence a post card, or even knock on their door, and attempt to explain the issue, and to offer them a much higher frequency (new) baby monitor perhaps in the 900Mhz or 1.2Ghz or higher realm and in the process eliminate yet another annoying major source of desensitizing man made noise  that is too close to 50 Mhz near by my home location.

The reason 50, 144, 222 and 432Mhz are also being scanned is because Power Line noise tends to show up in these frequency ranges quite well (at least around here it sure does).  This is the PRIMARY reason for this entire project to start with.  

This application records rf noise levels in 5 RF frequency ranges:

  • 49.7-50.0 Mhz
  • 50-50.3 Mhz
  • 144.2-144.5 Mhz
  • 222.3-222.6 Mhz
  • 432.1-432.4 Mhz
So I'm getting noise floor readings for 300 Khz in each range noted above.

The Nvidia Tegra TK1 functions as a GPS, COMPASS monitor getting Lat/Long readings, and AZ/EL/SPEED data while I drive and logs that data to it's attached and NFS shared data directory.  The TK1 also provides the Web-GUI (graphical user interface).

The Odroid XU3 (which by now I've totally fallen in LOVE with!) has the 5 RTL Dongles connected to a 10 port USB 2.0 power hub, and it takes Noise Floor readings constantly once started up and logs that data over the NFS to the TK1's attached SSD drive.

The combination of these two systems make up the "Driveby" application.  Making it possible to "Geo-Tag" Noise Floor measurements while in motion.  This means that it's then possible to MAP both the Lat/Long and Noise Floor readings on something called a "heatmap" which utilizes Google Map API.  Low noise levels show up as Green, and progressively turn to Yellow, Orange and Red depending on the signal strength at any given location.

So for example driving down a 'RF Quiet" road would look like a Green line, and driving into and RF noisy location would show yellow, orange or red.  Driving out of the noisy area would return to green again.  

Once the entire area immediately around my home has been mapped like this I can then drive out in progressively greater radius from home and improve the mapped data.  For example a few miles from here are some very high power transmission lines, all around this old power line infrastructure region of the state are problem areas.  Without something like this to map those areas I think it would probably be nearly impossible to really know what was causing my 'locally' high noise floor (frequently above s9 @ 50 Mhz in several directions).

Once I have mapped the bad locations, I can then return with even better equipment and pin point the actual source of the RF noise.  Whether it is someones Home, or some power line transmission equipment, or a street lamp, or god knows what.  

It's fairly easy to drive around with a radio and your ears and spot areas that are bad, but having an automated system to listen, and log everything while you drive is WAY more accurate, way safer to actually do, and definitely more convenient.

A system like this can be used for all sorts of things not just what I'm using it for which is really a very high level very simple noise floor recorder.  

SEE ALSO (Next Steps)