Radio Direction Finding

[PA3BNX]

Hello Every Body,


Happy New year 2014 to all.


I have been programming to get also elevation data from the
4 antenna array.

And that works because a transmitter at the horizon gives maximum dopplertoneamplitude
en if the transmitter is right above the array then there is no doppler tone left

so 0 degrees = max dopplertone and 90 degrees above  is zero dopplertone.

So I created a form with a elevation first kwadrant meter.

The slider is for the reference when the transitter is on the floor.

The amplitude diff is a sin function.

In the rim of the elevation meter is also a averaged red bug.

This should be very handy if you are hunting a balloon fox hunt.

Soon version SoundDoppler142 wil be on our sites.

Happy Foxhunting/experimenting this year.

[EA4FRD]

Dear PA3BNX,

First of all thanks sincerely for your nice job. It is really great everything you are doing for the ARDF.

I have a question that maybe you can help me. My idea is using your equipment for 27MHz in the car. I have been checking your software using a PIC as square wave generator (600Hz) for creating the switching signal, and as switcher I use a Chip RF chip switcher (instead of the diodes). As antennas I use 4 mag antennas, which separation is maximum 90cm (shaping a circle of 127cm of diameter)on the roof of the car. I see(heard) the antennas swithing, and the audio switching signal coming from the Rx seems fine. However If I spin the car, I don´t see any variation on the angle of arrival, keeping all the time in the same angle.

I have been checking the circuit and everyting seems ok. I am thinking that maybe one antenna is somehow much better than the others...but I do not see that in the oscilloscope (audio signal). Do you have any solution? Did you find that before? Something else I can do is filtering (with a Switched capacitor filter) the audio signal before conecting to the PC.

Thanks for your help.

Carlos.

[PA3BNX]

Hello Carlo,

If one antenna is not working it should give wrong bearings all the time.
after calibration.

Does the reference frequency read okay ?

See the menu Edit InputXY screen in SoundDoppler.exe

The upper-channel must be the reference signal about 300 to 1000 Hz orso
The lower channel must be the audio from the RX.

Also do check the sql (Squelch)
You must use a RX in FM mode ofcourse.


It happens that the referency and audio signal are changed from Left and Right
You can switch that on the soundcard hardware or use menu Edit Change left and right
in software.

Also make shure the reference frequency is the same as the doppler tone frequency heard from Rx when
signal recieved.

To check the antenna array is simple

Use a 4.5V battery with a 470 Ohm resistor on the + in series with a control line
and listen to the Rx on each antenna by just powering one control antenna switcher line.
You can easy check every antenna and cable this way.

You use a chip switcher

Important is that it leaves the not connected antenna unloaded.
Most chips I saw do terminate them with 50 ohm orso...
Thats bad because not used antenna's may not take RF energy from the rf field because of distorsion of the
wave front.
Thats why we use diodes and not switching chips.

Don't forget to ground the mag whipes very good to ground of car roof.

So maybe wrap some alufoil around the magnetic feet whipes to get more capicitya (Lower Xc) between
carroof and coax cable shield at antenna feet.


In the new versions sounddoppler 141 an 142 there is under menu Info an Antenna Array Calculator too.

Hope you get sounddoppler working okay now soon.

Does the PIC  output softswitched and overleap pulses
like our SuperSimpleSoundDoppler de Luxe does ?
(The one with 4 transistors after the 4017 chip?)


The new version SoundDoppler142aALL.zip is now on the PI4WAG site.



Succes

PA3BNX

[EA4FRD]

Hello PA3BNX,

Thanks for the nice email. Currently I cannot check my development, but I will do it asap, so the antennas. I chose frequency equal to 650Hz (by the PIC aka square wave generator, which I do not filter or smoth. Therefore pure square signals to the switcher) and as far as I remember, both channels (left and right) had the same frequency. BTW, although the filtered square signal generator was still in the scope (triggered by your software), the signal coming from the Rx was moving, as it was not triggered.....is that wrong?. On the other hand I use a switcher in a chip, which put the unconnected input to 50Ohms ( I think it is the best way to avoid re-rediation). In any case I want to check the diode-switcher too with a soft switched and over-leap pulses (as you proposed)

Moreover I must re-enforce the ground of the magnetic whips.

Thanks sincerely again for the answer, and I let you know as soon I have any answer.

Regards.

Carlos.

[Wolfy]

Greetings from North Carolina USA
K4GHL here, and I just wanted to say thank you for all your work (before I dive into building your stuff that is hihi)
I have read a lot of your posts, and am truly impressed with your dedication and continued support of your project!!!!!

I have built the Ramsey DDF on a breadboard, and about tore my hair out doing so (nothing like having one part left to place and having two parts left over, yeah, I missed something somewhere), so we will see how well things go with your set up

Just wanted to say thanks, keep up the great work!
Gary K4GHL

[PA3BNX]

Hello Every Body,

I found very nice site for a doppler direction finder

Dopplerjev iskalnik smeri
http://matrix.uni-mb.si/projekti/objava/vsebina/91/




All circuit and sources are in English on their sites.

I think it only needs softswitching so just ad 4 transistors to it.
See my supersimplesounddoppler de luxe circuits hi.

The Doppler gets much beter with soft switching
for weak signals and strong adjacent channel signals.


Further I saw that DopplerSys has software for an Android Smart Phone

http://www.dopsys.com/software/MPT%20User%20Interface.html

So Happy Hunting and Building

[PA3BNX]

Hello Every Body,

Now I retry to get the crossloops and sense antenna running on
my sounddoppler software with an Am radio on abt 3.6MHz

The two loops are tuned by separate C's

The meaning is that a loop + sense antenna gives a 1 + cos(phi) pattern

Bij switching the loops + sense I get four directions and these can be detected
bij SoundDoppler running with SinCos(Correlation detector).

So any advice welcome

I am building now the new electronics for it see the diagram below.

The core is something like t50-2 with trifilair windings 3 x 8 to 10 turns I think.

[HUTCOMINT]

 PA3BNX:

How much of these circuits do I need If I'am using a RTL-SDR?
I was thinking I might need only the antenna switcher, but then I see it has a 5-pin din that goes to God only knows where.

Thanks.

[PA3BNX]

Hello All,


You  do need a reciever with FM for the doppler

It's not possible Yet to do it with just an SDR DVBT T820T
Because you have latency in the I en Q stream from the stick

So you need a separate FM RX
And a generator like the 4017circuit and a antenna array switcher and 4 antenna's

The 5pin Din connector is for the control conection from 4017 generator to the switcher unit
Every wire in  the 5 pin din switches just an antenna on and off through the diodes on the antenna switcher
So 4 wires and earth wire

It's all in the program zip file SoundDopplerAll142a.zip


Today I did made pictures of the CrossLoop with sens antenna for 3.6 MHz
with the soundcard interface
This must run with an Am 3.6MHz reciever
It works quite wel even indoor hi.
See picture below.

[DH8DL]

Hello Every Body,


Here I send the lower part where the
PLL RF and softwitch pulses are made.

These boards are connected by wires close together.

There are errors in this PE0SSB layout. Actually it's 1 error which is repeated for all 4 Antenna Switch logic Controller circuits. I found out when i built this DDF96 3 years ago.
The Errors on this board are.:

R43 Needs to be connected to R10, not to R11
R44 Needs to be connected to R22, not to R23
R45 Needs to be connected to R16, not to R17
R46 Needs to be connected to R4, not to R5

Please check the circuit (from the PE0SSB Website) with the layout of this board and you will see.

Here is a Picture of the corrected Version.:

[PA3BNX]

Hello Every Body,

I myself have a okay version ASW board without the errors described above.

You can get this type of switcher working better with
dipoles if you ad a way to disconnect the earth of the coax
at the feedpoint of the 4 dipoles if antenna is not connected.

Having the coax shield connected while antenne is off can give
near field distorsion because half of dipole + half coax shield is resonant
and eats RF spectrum and distorts.

So any one has out there has a tip to add this option easy ?

Could be handy if you have a stationairy 4 dipole array.
and using this ASW (antenna switcher).

[hiishaam]

Hello : PA3BNX

First, Thanks for the great program SoundDoppler

I have 2 questions :-

1 - Can I use the program in band of 88 to 107 (FM Station Band) to locate any transmitter in this band

2 - How do the program do the DSP functions? I mean does it use correlation to get the bearing or zero crossing detection?

[PA3BNX]

Hello EveryBody,


The program can use SinCos(sometimes called correlation) or Zerocrossdetector.

I think that the SinCos detector works best..

Try under demo-mode 2 and the xy-screen the Adjust button
Than you have a test generator to play with the input hi

Just right click on the pelorus to change the sincos/zerocross detector mode.

Yes you can use it for 88-108MHz.

The reciever must be wide band FM
The doppler antenna must be adjacent 1/4 distance to get as much doppler tone as possible
compared to the music deviation.

There is under menu Info a Doppler_array calculator now

I did draw a 8 antenna SuperSimpleSoundDoppler de Luxe

If you use a stationairy antenna a 8 dipole works the best

The 8 dipole array switcher schould have large chokes in the switcher
because the are all parallel  at 145MHz and 1uH a choke has about 910 Ohm.
So 910/8=133 Ohm

Thats eating some of the recieved input power.

So use bigger ones like 10uH or 100uH in the 8 doppler array switcher.

The picture shows a 8 dipole doppler array with just the 4017 de luxe for 8 antenna
from DL3DW

Today 20-04-2014 Found Errors in 8 switcher circuits.

In the new 8 x switcher unit you can remove one diode 1n4148 in the middle
and you should replace the choke in the antenna feet with a 1 k resistor or something.
I will update the circuits soon.

[PA3BNX]

Hello Every Body,

Here is a design for not a doppler

An Am peiler with 16 led pelorus with
2 color leds from green to red indicating much or less signal in that direction
Already from 1993

http://www.ab9u.com/references/Willenweb%201993%20Schematics.pdf

You can do very easy Am direction finding with my software
and the SinCos detector and the plate antenna
Or use just 4 directional LPA's and just the super simplesounddoppler with an reciever
with AM detector.


Here they do it with just 16 stiks that form directional antenne and rotate it.
All the  leds light up from light red to light green indicating signal strength.

Nice to see and nice idea...

[PA3BNX]

Hello Every Body,


He is my proto drawing of a HF Radio direction finder with 2 aperiodic loops
and one sense antenna.

I am going to build this one to how it works.

I want to have a HF Direction Finder for HF without tuned
loops.

Today I show you guys some pictures of the above circuit build
R958 inside the PVC flexible tube and the red wire as Sense antenna.

[hiishaam]

Exuse me,

I Have some questions about SoundDoppler,

1 -  For antenna switcher circuit, I will use arduino chip (microcontroller) to perform the switching operation of the 4 antennas

2 - For FM Demodulation, I have a car mp3 as transmitter so I will use car FM receiver as demodulator and then pass the signal to sound card

3 - For sound card, Is any card has stereo inputs will do the job?

For all of the previous, Is this perform a good RDF design? Because I tends to add a RDF to my graduation project

The attached picture shows a block diagram of the design, Please give me your opinion

Thanks.

[hiishaam]

Sorry here's the design block diagram,

[hiishaam]

Sorry I forgot,

1 - Can I use the normal car antennas to connect it to antenna switcher as the receiving antennas at the FM band 88-108 Mhz.

2 - Can I use a sound card with one line input and generate a pure 500 Hz and then uses the WaveOut Mix in my sound card to compromise the use of UCA202.

Thanks alot.

[PA3BNX]

Hello EveryBody,

Yes it looks okay to me hiishaam.

I have not tried it with a broadband FM normal reciever

But I think it will work.

Arduino or 4017 circuit doesn't matter

Any soundcard that runs under windows is okay I think as long as it's stereo line/mic input.


Don't forget to have the vertical antennas need good earth if placed on a car roof

The dopplershift or deviation is a little bit small compared to wide band FM modulation..

So do not put the antenna's close to each other but about 80 cm or so in diameter I think.

See under SoundDoppler menu Info>Doppler Antenna array calculator.

To get easy all needed dimensions and parameters.

And find a place with less multipath and reflections hi...

Oh the sound card must be stereo so the 500 Hz and LF from reciever are sampeld at
exact the same time...

You can listen to the PC speakers bij playing the sound with the playback balans to the right
to hear not the anoying 500 Hz tone.

Take also a look at:

https://www.coaa.co.uk/dfplotter.htm

[avis]

Dear Sir.
  Have been observing your work and glad to see your success. I repeated some of your devices. However, to get a good accurate readings failed. Now I made a flat antenna to the AM. No questions on the antenna structure. Have questions about the control scheme.
In the attached file I'm interested data items are marked in red. As these items are structured? What are their values? Possible to use standard chokes? Where in the circuit connected to pins 2 and 6 MAX232?
Your guess RDF use on a small private airfield on the frequency 128.6 MHz
                               Sincerely yours, Michael.

 

                               

[jackdev23]

Hello everybody,
thank for this good thread.
I made a ARDF with Arduino Nano.
Check the prototype here
http://youtu.be/jm0Q4p4GudA?list=UU17SR_h8OR9WCBrsh_ak_sQ
PCB READY

73 IW2NDH

[PA3BNX]

Hello Every Body,

I see some have a problem with the max232
do not connect  or tap the internal voltages from the pins 2  and 6 from the max232


Nice to see the Arduino experiments IW2NDH.



I have done now a simple ne555 circuit to drive manually the AMPlate antenna

So easy only adjust the 4 stands turn switch NSEW
and a scanner or portofoon with S-meter while drving in a car
So no more stopping and using a Yagi or HB9CV for the balloon fox hunt.

Nice experimenting

 

[PA3BNX]

Hello everybody,

Subject: Doppler RDF on the 100 MHz 3 metres FM broadcast band


The problem with RDF on a FM broadcast TX
with about 150 kHz bandwidth is in the fact that the
standard doppler rotation tone is 500 Hz
With my standard SuperSimpleSoundDoppler 4017 generator (about .5-.6 kHz)
That's compared to modulated audio from the TX 150 kHz undetectable.

If I use mono FM TX with 150 kHz bandwidth:

At 100 MHz and a 500 Hz doppler tone.

With my 8 bits sound-card channel there is almost no
doppler tone to detect.
A 8 bit sound card has 256 samples so maximum amplitude contains 127 bits


(This is also true for a conventional doppler with classic 8 caps SCF)
(They have also a problem with the low pass filters in hardware)

150 kHz / .5 kHz = 300x if I take just one bit
for doppler tone then I still have  256 - 300  = -44 bits short.


I do not have enough bits to process undistorted FM audio by
the soundcard and detect the doppler tone.


This works better I think
Higher doppler rotation frequency and
bigger antenna plate diameter.
There is a maximum diameter with 4 antenna
(Of course it may not become unhandy large)
(See:  SoundDoppler.exe menu Info>Doppler antenna array calc)

Larger Doppler tone deviation by higher rotation frequency

I found that 4 dipoles and a doppler tone rotation frequency of
3 kHz gives 12 kHz doppler deviation on 100 MHz
Antenna diameter for 100 MHz about .93 metres
and optimal antenna plate diameter for monopoles 2.43 metres


150 kHz / 12 kHz = 13 steps

256 / 13 = 19x

This is possible with a 8 bit sound-channel.

(You must set the sample rate higher or the same as 22050 samples per second)

It's simple to set the multivibrator on about 4 x 3 = 12 kHz
by change the 15nF by 2n2

(Divide all by 3 kHz /.5 kHz = 6x)

In the SuperSimpleSoundDoppler de Luxe also change the 1n5
by 220 pF

Also change the 3x 100nF lowpass filter cap's for the reference frequency output in 3x 10nF

With the AM-Plate and Correlation detector mode this is different.

If I create on a FM broad cast RX a broadband AM detector
just before the AM limiter then I have excellent AM detected modulation.

This demands a broadband AM detector added to the WFM detector

Hint:

Maybe it's handy to modify an 'old' mono 12v car-radio with an extra
AM broadband detector because car radio's are well shielded and have
a coax antenna plug.


73's

[YD2WPE]

Hi,..PA3BNX,...i search a sound doppler program,...where could i found.,.?

thanks before

[PA3BNX]

Hello EveryBody

My software can be found on:


http://www.pi4wag.nl/projecten/doppler-peiler-radio-direction-finder

Download button at bottom of page