Interference detection

[shahram]

Masters
Anybody has any instruction on method of finding interference source location by any spectrum analyzer ?!

BR
Shahram

[riverstreamer]

Original posted by shahram at 2008-8-10 14:46 http://www.5inetop.cn/images/common/back.gif (http://www.5inetop.cn/redirect.php?goto=findpost&pid=19526&ptid=1233)
Masters
Anybody has any instruction on method of finding interference source location by any spectrum analyzer ?!

BR
Shahram

Dear
It depends on your S.A. model an features, but basically you need a simple S.A. which is more recommended to be portable.
S.A. is a good strong device who each expert like to use it for coming assure of frequency clearance in some cases.
Don't forget that S.A. sees some carriers in mobile Band(the band which you want t do checking on it) that Test phones (like TEMS pocket) don't see that(phones see 200KHz steps), So by using S.A. you can Scan & Sweep frequencies to find any CW or non-fixed crrriers which surely affect on mobile channels and by Cross & Circle driving, you can find the source on power level.
About standard mobile carriers you can use this to find unauthorized used ARFCN by other operators like what you do with scanning mode of TEMS.
In addition you can see and find ISI by getting help of S.A.
What is important is that S.A. may be used occasionaly but at that time having a S.A. in hand give more help and speed-up finding the problem source.

I hope what I explain be helpful for you. There is not specific or advanced subject for Spectrum Analyzer; Just during working with it you need to have communication/Wave issues in mind for getting decision.

Yours/
riverstreamer

[shahram]

thanks riverstreamer.
your comments are useful,and we can simply find the interferer signal freq and...etc specifications,but I am looking for a solution to find the direction and geographical location of interferer signal source.
Could you please give more explanation on this subject,do you have any document or maybe a case study?

BR

[ Last edited by shahram at 2008-8-10 18:33 ]

[riverstreamer]

As military or intelligence services do this duty with simple S.A., you are forced to use driving method to come near the sources. in some cases you do like this with general TEMS drive test tools to find problem.

In these conditions going along long streets and Crossing them will show your target area and by driving in circular method in that area, surely you will find the source.

In advance S.A. and sweeping tools there is this ability to show the location of specific power source, but this will be available in the case that you have a multiple set of sweepers which are in connection with each other and analyze the area and give you the result; I don't think you have such new high-tech tools in hand.

BR/

[shahram]

thanks riverstreamer
I got the idea,

/Shahram

[hassen]

This is your question
to find the direction and geographical location of interferer signal source.
It is possible
first try to make measurements in three different location arround interferace area
for each measurement point you have the coordinates long_lat and you have rxlev of
undesirable frequeny.
now you have three circles
each circle corresponds to the values measured on centre the fixed coordinates
according your propagation model
seek the intersection of three circles, and you can locate the problem .
Some mathematical method and the problem are solved friend.

bye and good luck

[ Last edited by hassen at 2008-8-10 21:34 ]

[shahram]

thanks Hassen
Like the method used for finding earthquake center point!! but it needs very accurate synchronization.
Anyway I think I can do something with this idea!

BR

[ Last edited by shahram at 2008-8-10 22:12 ]

[hassen]

Hi
The method is simple :)
according to your model of propagation you can estimate the distance.
of course you have max and min and you can have the average distance( max+min)/2
the equation of a circle is (X)² + (Y )² = R² the intersection of three circles gives a point.
convert geo coordinated on metric ,I mean you should have x(m) ,y(m) , Rmax(m)
and x(m) ,y(m) , Rmin(m) and x(m) ,y(m) , Raverge(m) for each location that you receive
signal ,and from this rxlev that you estimate the distance.

now you have 3 equations whose variables are known
for example
X1 Y1 Rmax
X2 Y2 Rmax
X3 Y3 Rmax
find the intersection of these 3 equations and you get 2 points the first is correct the second is imaginary I mean if the point is outside the area forget.normally for each point you have x1 y1 in meter convert en geo and see in the map.
same method with R=Rmin and Raverage.
finally you get a triangle ,a region of the source of interference.
send a team to make drive test in order to confirm your result:
BR Hassen

[Stantheman]

Hi Shahram try Radio Mobile http://www.cplus.org/rmw/english1.html it is an extremely capable piece of FREE software and it has a Fox Hunt feature that you can use on top of the loaded DTM and overlay maps (which it can download from Google, Yahoo, MapPoint, Virtual Earth etc .. makes very nice map overalys). It also exports directly into Google Earth. If is awesome software, not suitable for cellular planning but brilliant for land mobile radio, links etc .... see the related links page http://www.cplus.org/rmw/links.html for lots of other sites that support the program. You could use the Fox Hunt feature on a mobile laptop to triangulate your source of interference using a directional antenna and appropriate receiver. Yes it is FREE (hard to believe given its capabilities) and so are the DTM maps (SRTM, BIL etc ..) and overlays. You can also use 1km Land Cover data. PM me if you want some help with it. Give it a try, you will be impressed.

[Stantheman]

Shahram, have a look at this as well, it is Ham Radio SW specifically for Direction Finding, haven't used it but it looks interesting http://www.pa7rhm.nl/downloads/screenshots/screenshots.html#UIDFPlot http://www.pa7rhm.nl/index.html http://www.pa7rhm.nl/downloads/uidfplot.html

[shahram]

thanks everybody here!
I think it worth if you found any doc related to interference put it here in this topic.
BTW,thanks again

/Shahram

[da_manole]

Masters
Anybody has any instruction on method of finding interference source location by any spectrum analyzer ?!

BR
Shahram

http://www.4shared.com/file/93230959/7e4f2f76/Fundamentals_of_spectrum_analysis.html
In practice you need an omni and an directional antenna .also you need a passband filter to protect your analyzer( if you overload the analyzer it can create IM itself).In crowded places it's good to have an omni antenna because you have a lot of reflections and you can locate easier the area .you need a lot of experience to work directly with a yagy antenna .
About spectrum analyzer it' good to have with preamplifier inside(if not you need an external one).once i found an interference 100 km away, 10 mw in a top of a hill.
If you need more info pm me.