Author Topic: Radio Direction Finding  (Read 22979 times)

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Offline PA3BNX

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Radio Direction Finding
« on: January 05, 2012, 08:34:45 AM »
Hello to all,

I am working on a VHF Direction Finder working
on the PC soundcard  with GPS (etrex) and plotting real time
on maps.

So see the pdf file for circuits

And the zip file for other design from do2scf

Let me know what you think of it

Any comments ?

Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline Psi

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Re: Radio Direction Finding
« Reply #1 on: January 05, 2012, 10:09:09 AM »
Nice, I've always wanted to build something like that.

Does the direction finding work equality well for signals that are meters away and signals that are a far away? (like a few km. Assuming the signal is strong enough to be received)
Greek letter 'Psi' (not Pounds per Square Inch)

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #2 on: January 06, 2012, 05:46:41 AM »
Hello everybody,


It works best if the antennes are positioned free and high and outdoor.

Other wise you have multipath and reflections.

You must have a minimum distance from the tx antenna array about 3 a 4 meters.

The distance can be of cource depending on power , height and annnas of transmitting station up to

20 to 50 km.

Practically speaking the optical horizon distance.

The program MyMapping.exe has also a optical horizon calculator witch can plot
range circels on the map

d=3.58 * sqr(h1 + h2)

d in km
h1 and h2 antenne heights in meters.

 
« Last Edit: January 06, 2012, 06:15:32 AM by PA3BNX »
Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #3 on: January 09, 2012, 04:52:19 AM »
Hello Everybody,

I did post the antenna array for the doppler

It's a alu round plane with wooden base

and 4 whips of about 50cm welding wire 3 mm

Note that the antennas are not on the edges.



Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #4 on: January 10, 2012, 08:25:07 AM »
Hello Every Body,

I am also building a HF Peiler for the 80 meter amateur bands

That uses the catcontrol from a Yaesu FT817 or FT840

That reads the RSSI an switches the magloops on of with the Sense antenna.

This project is still under programming and construction

So hint and tips ?
« Last Edit: January 11, 2012, 05:26:50 AM by PA3BNX »
Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #5 on: January 11, 2012, 05:33:34 AM »
Hello All,

I put a smal picture of MyMapping.exe

My vb2005 program that works in conjuction with
my SoundDoppler.exe

Today I did some programming to get the kml file for Google-Earth okay to.

Mymapping can print on bmp, jpg or png picture maps
almost in realtime the Doppler headings with many futures for getting cross line points
and gps inputs.

It can also put optical range circels fully automatic on the maps
ans speak the bearing like TomTom when driving and fox hunting.

Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

HLA-27b

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Re: Radio Direction Finding
« Reply #6 on: January 11, 2012, 05:58:46 AM »
Quite intriguing.  What do you reckon the angular resolution to be? Anything that can resolve direction within 15 degrees with a sound card is pretty impressive.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #7 on: January 11, 2012, 08:06:24 AM »
Hello Everybody,

How accurate is a doppler bearing with the soundcard.

Well that depends on free rx site and less or no reflections
So the antenna array has to be free.

Secondly the amount of antennas and the circel diameter and how well
GP antennas are grounded at there base feet to the main plate.

The antennas must be omidirectional so not on the edges of the ground plate

The soundcard accuracy depends on the samplerate of the soundcard
in software and the doppler rotation speed frequency.

The more samples you have in one revolution the more precise it is.

You can easy have 50 to 100 Taps on 500 Hz so 360/50=7 degrees already.

Dont forget the averaging in the software that increases the precision.
Remember there is many time modulation on the FM carrier.


So for 4 whipes you can get about 5 to 10 degrees precision easy if there
are no surrounding reflections.


Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #8 on: January 12, 2012, 07:12:12 AM »
Hello Every Body,


Today I thought would it not be nice if I could modify the
NMEA string $GPRMC for the GPS mouse (GPS Yellow etrax)
So that it has not the GPSCompass but GPSCompass + DopplerHeading

There are many programs that can show GPS direct on a map.

So I started writing a modifying routine that
outputs also on a com port the modified $GPRMC

Example:

$GPRMC,124344,A,5157.8111,N,00534.2454,E,0.0,30.0,110112,1.1,W,A*36

So modify 30.0 compassdegrees with the doppler heading.

and then create a new CRC after the *

So my new GPS.exe program wil read and extract the $GPRMC from the
GPS mouse and modify it and send it out on the same or other comport.

So I have again a new option for my software to build in.

Are there more Visual Basic Coders on this forum ?
 
 :o


Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline sonicj

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Re: Radio Direction Finding
« Reply #9 on: January 12, 2012, 12:14:06 PM »
neat project! my dad and his ham buddies went hunting a rogue transmitter a month or so ago. they drove around for at least a couple of nights with a yagi and spectrum analyzer before they found the culprit.  ;D
-sj

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #10 on: January 14, 2012, 07:01:59 AM »
Hello All,

I worked hard in coding to get the option
of modifying the $GPRMC string working in

my GPS.exe program.

I am still not ready with the DDE link stuff.

DDE is obsolete Dynamic Data Exchange stuff but
because my SoundDoppler en GPS are written in it I have to get it working.

Of cource I also will write this option in my New SoundDopplerNet.exe

But thats not finished / working yet.

I show you here a screen dump af a very intresting and good working

VHF soft-antenna-switcher for the doppler.

That is the datong doppler circuit on two boards.

All signals is done is through 1 coax cable witch does
do the RF, DC-powersupply and Reference for switching the antennas.
Every antenna has a wide band RF amplifier and then the output is fed throug a PIN diode
to the summer.

The advantage is that now you cannot hear in a nearby reciever the commutating
antenna whips acting as reflectors and because ist softswitching
instead of hard switching you can hear less loud stations.

« Last Edit: January 14, 2012, 07:09:39 AM by PA3BNX »
Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

HLA-27b

  • Guest
Re: Radio Direction Finding
« Reply #11 on: January 14, 2012, 07:14:51 AM »
Cool job

May I ask what are the pcb sizes and hole locations are you using?
I am currently working on pcb assemblies, holes, fixing arrangements etc, hence my curiosity.

Offline PA3BNX

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Re: Radio Direction Finding
« Reply #12 on: January 15, 2012, 05:19:43 AM »
Hello All,

Here I post a picture off the Input XYscoop found in SoundDoppler.exe

The upper line is not quite a sinus but a little distorted with
the SuperSimpleSoundDoppler design.

I want some hints how to improve the sinus with minimal extra parts.

and enough output to drive the soundcard line input.

I know my software only detects the zerocrosses to get the frequency and antenna 1 position.
But it looks not nice.
 
Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

Offline PA3BNX

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  • Posts: 107
  • Country: nl
  • Trying to learn better programming and designing !
Re: Radio Direction Finding
« Reply #13 on: January 15, 2012, 05:23:10 AM »
Hello All,


The PCB sizes of the datong antenna switch are about 10 bij 10 cm

They are put above each other and connected through wit some wires.

I have not made the PCB myself I did have bought some years ago
Just the Prints.


Greetings,

Lodewijk

Credo:

Home brew projects:
Build/Design  with minimum hardware
and maximal software.

HLA-27b

  • Guest
Re: Radio Direction Finding
« Reply #14 on: January 15, 2012, 01:56:22 PM »
The PCB sizes of the datong antenna switch are about 10 bij 10 cm

They are put above each other and connected through wit some wires.

I have not made the PCB myself I did have bought some years ago
Just the Prints.


Thank you, 10cm X 10cm seems to be very popular naturally.


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