In world of HAM there are infinite forms of determining from where , in which way , comes a transmission.
The conventional methods like Yagi antennas of 2 , 3 or more elements constitute a good election to the hour of seeking the direction toward to put prow when it is considered distant signals .
While one is beginning to be aproached the emission zone ( 300 to 400 Meters ) The indications of maximum signals start to be more erratic due to the multiple rebounds presence in various objects , such as , trees , buildings , electric lines , etc.
Neither saying it's being in the last meters ( 100 or less ) the measurements become impossible . Then we have to use RF attenuators pasive or active , to minimize the indications the maximum possible to discriminate which is the correct sense .
Yagis with field intensity measurings is another choice , but be careful , our hidden friend use to changing the transmission power , therefore when we believe he is very near , in the next transmission we can lose him.
Then they come in complexity order , the antenna to detect the " zero " of the signal .
A combination of dipoles with inverted phases it's a good alternative , more reliable than the Yagi.
Another example of this kind of antennas is the old and never measured Aro or Halo , which it must be in perpendicular form in transmission sense , and we'll obtain the minimum indication.Another good option.
But both present , in smaller degree , some defects of the first mentioned : in the last meters , the experience and the trickery may be more than the antenna , because they dial for any side .
And it's here where the devil inserts the tail , where appears the star of the last years : THE ELECTRONICS.
The easiest and very effective is a pair of dipoles conmuted by a small oscilator in a frecuency between 300 and 800 Hz.



The oscilation prints in the audio an agreed sound in frecuency that , when the dipoles are both faces , to th some distance than the transmisor receive the signal in the same phase point , therefore the imposed noise dissapears .
When we begin to turn in any side our dipoles , the phase point in dipole 1 will change respect the dipole 2 and that phase difference will be made audible through the speaker .
The main advantage of this method is that it's able to discriminate the direction without importing the distance that separates us from the source of transmission , neither the power which issues , since we are not seeking signal variations but audio variations .
There are Kit's for preparing with this sistem and until aven the most elaborated bring a pair of LED's which indicate in which way we have to move ( right or left ) .
But not all are roses . Audio variations because of modulations , continuous tones , etc. , could provoke erroneous marks due to doincidences in audio frecuences wiht the oscilator which conmute the antennas
Another choice is that this systems indicate only right or left and one must to have certain practical to discern between forward and back , since a transmission which we have detected the correct sense could be toward as well as toward bacward .
Also is to explain the nerves situation of that moment so that something very simple become something terrible .
After being experimented all what is previously exposed and being obtained the most various results in clasification positions in competitions in that zone , we arrive to the conclussion that was the moment of something better , something that not us so many complications , something more comfortable , and that something was existing : THE DOPPLER .
There it was born waht first was called " SPUTNIK " since the equipment form that was going to be on the vehicle that transport us .
We had the idea of putting eight dipoles to obtain more presicion and sensibility than the four quarter wave , as bring some commercial equipment and after we crown it to the design wiht a filter for the indicative phase signal that turned out to be a marvel by it's simplicity and efficiency .
Voices , tones , rare noises and the LED was always indicating towards where we had to go .
A brillant equipment , which never afford experimented happiness and victories never dreamt by us during six unforgettable months .
But we still had an inconvenient . Not always was possible to arrive with the vehicle until the transmiter or until the fox's hideaway .
It was there when it appeared " the little boy " , The Doppler of hand , bautized " Enterprise " by its notable seemed with the famous TV series ship .
It is not a dream , a Doppler that fits in a hand .
Both of vehicle and the hand gave us the standard of the fact that we had arrived to obtain something that privileged ones had .

Now we know that it operates , we decides to draw it to the light so that all could experience it .

As final commentary i want to add three things :

First : It's not the automatic pilot of a car that will carry us direct to the site while we are drinking coffe and eating cookies .

Second : The proliferation of this class of appliance will begin to transforms the competitions into literal car careers . We have to be prudent . Even though is a competition we should not let being heartfelt and loyal with the adversary , because it's considered an entertainment .

Third : We want to thank all those helped us in the development and construction of the equipments , as thus to thank to all our companions the cordial treat that always excused us .

AND NOW ..... BUILD IT !!!!!

PD : I'm sorry , my english is very poor .-