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Triangulation system

A

a21

Member
Feb 7, 2009
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Hi,
I want to make my triangulation system in UHF band using 3 static receivers. I searched google for some info, but everything about triangulation that I found uses signal strength to determine the distance to the transmitter. But the signal strength depends on too many variables and this method is not precise. What other can I use to build the system? What other parameter is linked with the distance to the transmitter and it don't varies too much?
 

How about using a highly directional antenna at those receiving stations. It's a fairly standard sort of method of finding other stations. It requires knowing precise locations for each recieving station, and calibrating the azimuth of those directional antennas. The more 'fixes' that can be had, the more accurate the resulting location. Never going to be super accurate, as in a few feet, but can certainly get within several yards, sort of. Then, plotting the whole thing on a map. The only requirement for signal strength is enough to hear that misplaced/displaced transmitter. Signal strength is a ~very~ unreliable determinant.
- 'Doc
 
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Sounds like an old fashion 'fox hunt'. Tactics are important. If you are trying to find a
'pirate station' that is elusive; one need to engage the station in question with a friend on his base station - and have a mobil rolling w/o talking - and use a directional antenna on the vehicle.

Or-just mount the antenna on one end of the vehicle so that reception becomes stronger and weaker recieve depending which end has the antenna. It becomes directional by default this way. I tracked many a station using this method. The trick is to stay with it, and get the station in question busy long enough to get close. The base station/friend will need to do this, so that you aren't observed - that is key.

When you get real close, loosen the PL-259 on the mobile recieving radio, so that relative loss of signal strength can get you even closer - and then you are there. Works every time; so long as your frind on the base station can keep the hunted station talking and he doesn't know you are hunting him. So - if you must talk to your friends's base for any reason, use your cell phone - but DON'T use uyour radio and give yourself away. Setting up a couple of stations and radios and people wouldn't get you close enough - if that is what you are trying to accomplish. What other reason would yu have - a21?
Just two cents worth...
 
How about - anti jamming system. That is what I want. But I don't want it mobile. I want it static and the triangulation will be done done PC and shows directly on the map. I have no problem with the software, but have problem with the hardware :)
Ok. I will you directional antenna, but in what direction to put it for each receiver? I in this way I will measure what - angle?
 
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HAving two stations rather than one won't stop the jamming. Radio is run on a system of courtesy on any given frequency. If someone is jamming you, you have two distinct choices.

First choice is to call the FCC and complain about unwarranted radio interference from a station operator. This doesn't always work; as they ususally respond when citizens who aren't radio operators complain about some operator the interferes with their TV or stereo system because of too much power or an improperly tuned station throwing off too much RFI. They sometimes respond to that if the complaints continue to come in.

The second choice is to track down the station yourself, as this shouldn't be too hard to do at all if they are constantly broadcasting a signal. I already explained how to do that. Then, send that info to the FCC by email - or phone them up and tell them the address of the offending radio operator. That makes their job easier, as it is the job of regular Ham operators to find stations that aren't complying to FCC regulations and send them a notice by US Mail. If a Ham Station Control operator does't send the notice, yu can send them a OO card yourself, and notify them as to why you sent it. Look it up on the internet, you can find out more as to how this is dione. You can also talk to someone at the FCC that can also give you some useful advice. It isn't worth getting in a verbal scrap or getting physical with the offending station operator, it will be counter-productive for you and you can easily find yourself in jail for something that doesn't add up to a hill of beans. Let the FCC take care of it; or find a Ham operator that can verify your claim and he can send this offending operator the appropriate 'OO' notice.
http://www.arrl.org/FandES/field/org/oo.html

Am I close to what you asked; or am I way out in left field?
You decide...
 
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Referring to your first post and 'triangulation'.
If you know two points and the distance between them, you can find a third point by measuring the angle of that third point from each of those two points you know. Since you know the distance between those two known points, and the angle of the third point in relation to those two other points, you can find the distance to that third point. When you have a known angle and distance from a reference point, you can plot the position of that third point on a map. That's geometry dealing with the characteristics of a triangle, and why it's called 'triangulation'.
The 'problem' with doing any of this with radios is that the process isn't very accurate, deals with how 'sharp' of a directional pattern the receiving antenna has, and none of them are very 'sharp'. So, the larger the number of receiving stations, the more positional data you have, and the end result is narrowed down to some extent. To some extent, the larger the distance between receiving stations, the greater the angular difference to that 'third' point can be, which also tends to make calculations 'closer' to the target, sort of. That's a generalization and certainly not true in all instances.
You're certainly right about signal strength, it isn't a very good way of determining distance. The 'target' has to have a minimum signal strength or the receiving stations won't hear it at all. That's about the only requirement for signal strength.
I'm making some assumptions with this. The first is what I am assuming your question is. It certainly wouldn't be the first time I've misunderstood what was asked, so if this isn't at least 'close', please restate your question.
As for what could be done about the 'found' station, there's almost nothing a private individual can do legally. There's too many variables in that to even make a reasonable guess about, so I won't.
- 'Doc
 
Here is the real situation. I have 3 receivers. Someone is jamming me for 5-10min maximum and I need to find from where he is jamming me with radius of 30-50m. And he is jamming me from different locations in the city anytime. That is why I want static anti-jamming station, because I cannot react in 5 minutes with mobile rdf. This is my problem. I will do the software and maths. Just need to know what to measure and how it is linked with the distance or angle to the jammer. Sorry for my bad English, but I cannot explain it more accurately.
 
You're going to have to locate your three receivers quite a distance from one another (maybe a mile apart; more if this is a large city).

Then you need three very sharply directional, ROTARY antennas, one at each receiver. When the jamming starts, the three antennas rotate, looking for the direction from which the signal is strongest.

Then it's a simple matter of drawing a line on a map of the area from each antenna location in the direction of the strongest signal. Where these lines intersect gives you the location of the bad guy.

Spreading the receivers (actually the antennas) out is the key. If they're too close together, you'll wind up with three parallel lines, indicating the general direction but not much more.
 
The distance between the receivers is enough - more than a mile and this is ok. I thought about this rotary antennas, but I was not sure that it will Help, but now I am sure that it is ok :) For more accurate results the antenna must have more positions, right? I thing that 10 positions are enough. This is 36 degrees between each position and I think it will give an accurate result. But of you think that there must be more - please tell me.

I am thinking of this type of antenna - http://www.antennasdirect.com/91XG_HDTV_Antenna.html, because I am working in the UHF band (not TV :) ).
 
There are two methods of determining the position of a transmitter. One of them involves direction, angular displacement, the other involves time and it depends on the positioning of a number of receivers/antennas. Both methods depend on how accurately you can measure direction or time differences. The 'time' way is probably the most accurate now, but certainly wasn't in the past, and is probably the most used current method. Neither method is ever going to be absolutely 'accurate', too many variables, but it can get you 'close enough', maybe.
There can be more to it depending on frequency of use, equipment used in determining angles/times, and other considerations. It isn't simple. The best 'way' of doing this locating is dependent on need and equipment availability. Those are different for everyone, and just not possible for some.
- 'Doc
 
a21 said:
Hi,
I want to make my triangulation system in UHF band using 3 static receivers. I searched google for some info, but everything about triangulation that I found uses signal strength to determine the distance to the transmitter. But the signal strength depends on too many variables and this method is not precise. What other can I use to build the system? What other parameter is linked with the distance to the transmitter and it don't varies too much?
Click to expand...

Hi a21,

What's done in a fox hunt

In a foxhunt, triangulation is manually done using a map, a magnetic compass, a beam (directional) antenna and a receiver with signal strength indicator ('S' meter).

At the first location, the map is aligned to the cardinal directions (NSEW) using the compass. The beam is rotated till it points in the direction of maximum signal strength. On the map, a line (bearing) is drawn from the first location in the direction of the beam.

This is repeated in the second location.

The point of intersection of the 2 lines gives the location of the transmitter.

A third location is required only to confirm the location.

What you would need to do to apply the above and get the location manually

The following would be required:

1.A beam antenna at each location with a rotator and a 360 degrees/revolution angular encoder. The angular encoders would have to be zeroed with the antennas pointing due N.

2. A receiver with 'S' meter at each location.

3. A protractor for drawing the bearings on the map using the angular encoder readings.

Getting the location using software

1. Use GPS to get the co-ordinates of the monitoring stations.
2. Get the bearings from the angular encoders.
3. Input the above data to get the co-ordinates of the transmitting location.

Do hope the above information gives you sufficient clarity.

Regards,

Nandu.
 

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