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TUCoPS :: Radio :: rdf.txt

A Method for Radio Direction Finding RSC:




06/23/03

A Method for Radio Direction Finding
By:The Engineer    
___________________________                        

Disclaimer: Don't mess with HAMs.  Despite what some people may think,
HAMs provide a valuable service in times of disaster.  Also, if you jam
for too long, you will get cocky.  Then you'll make mistakes.  Then
you'll get caught.  Then you'll be in a world of shit.  The FCC *does*
like to make examples of the poeple they catch.

Many phreaks and hackers find radio gear indespensible.  It comes with
the territory of being curious about the nature of what makes things
work the way they do.  As we all foray into the dark side of that
curiosity, that VX 7-R, FT-90, IC 2800, or whatever other radio of your
choice becomes a source of learning and entertainment.  Never again will
Wal-Mart's two-ways be safe when you're sitting in the car waiting for
your girlfriend to come out of the store.  Never again will the person
in front of you be able to complete their order at the drive-thru
window.  Never again will the neighborhood kids FRS radios be the same.
You've got cab companies crossbanded, and the drive thru clerk is
screaming that "No, we WON'T do a cleanup on aisle 9."

But how do you keep from getting caught?  How do you keep from having
fun and then having the FCC take all of your radio gear?  Or maybe you
want to track down the girl with the cute voice on channel 7 or give
that loud mouthed "Radio Rambo" a chance to put his money where his
mouth is.  How can you accomplish this?

Radio Direction Finding!  With awareness of simple RDF techniques, you
should be able to stay ahead of most amatuer RDF'rs and out of legal hot
water.  By knowing the techniques they will use against you, you can
adjust your tactics accordingly.  "Know thine enemy", as Sun Tzu once
said.  That rings as true today as it ever has.

"But it seems so complicated!", you say.  Not so.

****First off, I'll explain a simple method of RDF.  Later I'll cover
ideas on how not to get caught.

*First of all, you need to get out and find the following gear:

1- A radio, either a scanner or transciever with a signal strength
meter.  It helps for this to be a bar-graph display, from what I've seen
that's all you'll be able to get nowadays

2- A dirrectional antenna.  The best results are with a Yagi antenna;
these look like a flattened TV antenna (The type on the roof, genius...)
tipped sideways.  (From this point on, called the "Beam").

3- A vehicle (Because it can be a bitch to track someone across a city
on foot)

4- A wheel man and a radio man. (It is possible to do this solo, but
trust me, it's easier with two people.  The wheel man drives and the
radio man spins the antenna, watches the sig. strength meter and acts as
the eyes when you get close)

5- A street map of the local area.  Hudson's is your friend, here.  

***Now that you have the radio mounted in the car, find a way to mount
the antenna so that the radio man can turn the mast while mobile.  A
fixed, rigid mount simply will not do.  One trick is to clamp a vise
grips to the mast, with the grips aimed to the front of the Anntenna.
Find a good high point and wait for the signal.

As soon as the person you're looking for transmits, it's the job of the
radio man to spin that Beam around as quickly as possible while watching
the S-Meter.  When it reaches the peak (that is, the highest point
before the signal drops off again) that's the direction of the signal.
The antenna (and the vise grips) should be pointed in the general
direction of the transmitter.  When you get a couple of bearings, that
map should come in handy.  Plot your position and each bearing, and
where the bearings intersect, that's where you want to be.  Right where
the lines form an X.  At this point you would drive towards the source
and pull out the tire iron, baseball bat or lead pipe (or whatever you
choose to beat the rogue operator with).  As you get closer, take
further bearings and make adjustments accordingly.  Soon enough you'll
run into problem #2, see below.

Naturally, it's the wheel mans job to drive, and take directions from
the radio man.  He should be familiar with the streets, intersections,
traffic signal, speed limits, etc...

A few problems you may run across:

1- Local Law Enforcement-They will be, to say the least, curious when
your beat-to-shit Olds Delta 88 comes rolling by the Donut Shop, Beam
sticking out the roof and spinning like mad.  They can be a slight
complication.  The best way to cope, in this case, is to cooperate

2- Saturated S-Meter-when you get close, that S-Meter will be indicating
full scale all around you, even with whatever attenuation settings the
radio has activated.  In this case, tune off frequency until there is a
dip in the S-Meter (Typically 20KHz up to 15MHz).  You should get that
peak when your bearing  is correct agian.  With this technique, you
should be able to narrow the location down to the street, or even a
couple of houses.

3- Apartment complexes-While this is tough, it can be done.  Sometimes
it's best to have a second radio, preferrably a handheld, with a short
(less than 2 inches) piece of wire in the antenna jack.  When you get
close, the signal will peak on this radio, too.

4- Gated Communities-Those holier than thou types can afford new gates
to their streets.  Floor it to ninety and crash on through...

5- Loss of Cabin Pressure-Put your head between your legs and grab your
ankles.  In the event of a water landing...

***With a little practice and a little skill, you'll be able to track a
person across a largish suburban town in very little time.  Our best
time so far has been across three towns (a distance of about 15 miles)
to an aparment parking lot in 20 minutes.  Along the way, you'll run
into trouble and find new techniques not mentioned here.


****How to Not Get Caught**** Okay, now that I muddled through the
explanation of how one technique works, here goes the important part...
A few methods of how not to get caught doing any of this:

First, keep your rogue (or pirate) station low profile.  Use small
antennas, or better yet check out a company called STI-CO at, strangely
enough, www.sti-co.com.  They sell duplexers that allow you to use your
cars broadcast antenna to transmit.  The more discreet your antenna, the
less you'll stand out.

Second, try to blend in with the crowd.  Remember the line in the movie,
"Hot Shots!", about how there's anonymity in a crowd?  It's true.  A
vehicle in  a mall parking lot is a lot more natural than an odd car
idling in Unlce Cletuses front yard.  You'll find that a car will blend
in better among other cars than it will in the middle of an abandoned
parking lot.

Third, if at all possible stay mobile.  Don't sit in one spot for more
than five to ten minutes.  Try to keep it around five minutes.  Some of
the best "Foxhunt Teams" I've seen can track a person across three towns
in under fifteen minutes.  The trick is not to be in one place too long.
As an extension to this rule, always have more than one escape route.
If you only have one way in, you only have one way out.

Fourth, don't fuck with a Leo.  Leo is my term for Law Enforcement
Officer.  Leo has a lot of brothers, and they're all itching to bust the
people that irritate them.

Fifth, monitor the local airwaves.  When there are several teams working
together, they may be foolish enough to communicate via the Ham bands.
If (or when) they get close they may start to let radio disipline slip
and start to chatter a lot over the radio.  Remeber, if they can hit you
full scale, they're close (Possibly L.O.S).  Also, it's a handy way to
keep Leo off your tail, and not be there if he stops for a visit.

Sixth, don't use your own unaltered voice.  The last thing you need is
them confronting you with tape recordings of your own voice telling them
they'll never find you.  Use the audio pin on the radios data jack and
hook it to a laptop computer.  Then you can play music, sound files
(Full Metal Jacket, anyone?) or whatever you desire with little concern
of being identified.

Seventh, vary your transmit power.  See that power setting on the radio?
Use it.  If you vary your power, it will be harder to "get a fix" on
your signal.  

Eigth, if you are jamming from an apartment complex and you have an idea
the "hunters" are close, DO NOT look out your window to see if you can
find them.  DO NOT turn on/off any lights in the room.  Don't do a damn
thing.  Sit there and act natural, talk natural.

Ninth, keep your transmissions short.  This gives the hunters less time
to spin that beam around and get the peak on the sig-strength meter.

Tenth, if you feel compelled to jam frequently, keep an erratic
schedule.  Don't jam at the same time every day,  don't jam from the
same place every day.  Hell, don't jam every day.  One time, transmit
for ten minutes at 8:30 on a Sat night.  Then wait a few day and jam on
a Tues morning for half an hour.  Then on a Thursday during lunch for
maybe two minutes.  The idea here is to keep the hunters off balance.
Don't develope a pattern they can anticipate, and don't jam with the
same activity every time.

***** It may seem odd, but I would recommend reading Sun Tzu's "The Art
of War".  It teaches basic principle of tactics, such as "If you know
everything there is to know about your enemy and yourself, you shall not
be imperilled in a thousand battles.", and "Be extremely mysterious,
even to the point of formlessness."

I hope that this article answers a few questions for you and provides
you with a little bit of fun.  Be careful out there.

(Next Time: Who invited you to this party line?)


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