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Author Topic: PI4WAG - Pseudo Doppler  (Read 72348 times)
M0ATZ
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Posts: 15




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« on: February 28, 2012, 12:51:16 AM »

Hello - I have a two quick questions about the most impressive PI4WAG / PA3BNX Pseudo Doppler software.

1. How does the calibration work? There is a 'slider' which makes an adjustment, but I dont quite understand what it does, or a 'Cal' button which locks on to a test signal and sets that as North. I'm interested in Calibrating the Doppler to Vehicle North, i.e. the front of the car is north, whats the easiest way to do this?

2. When I receive a signal through the Doppler I hear an audible tone from the antenna switcher on the rig audio. This isnt from the left channel input being played back through windows as I'm taking the audio feed directly from the rig itself as opposed to taking it from the sound-card, it appears to be the heterodyning of the two signals. Is this normal, is my circuit 'leaking' has anyone else experienced this?

Many thanks in advance, 73

M0ATZ - Colin
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WB6BYU
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Posts: 13341




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« Reply #1 on: February 28, 2012, 10:46:19 AM »

Quote from: M0ATZ

2. When I receive a signal through the Doppler I hear an audible tone from the antenna switcher on the rig audio. This isnt from the left channel input being played back through windows as I'm taking the audio feed directly from the rig itself as opposed to taking it from the sound-card, it appears to be the heterodyning of the two signals. Is this normal, is my circuit 'leaking' has anyone else experienced this?



This is normal - in fact, it is required for the unit to work.

Rotating the antenna (electrically or mechanically) causes the incoming signal to be modulated
by the doppler effect:  higher in frequency when the antenna is moving towards the source
and lower in frequency when moving away.  Since you are listening on an FM receiver, you hear
this modulation as a tone.  What the software does is to compare the phase of this tone with
the direction of the antenna to determine, for example, which way the antenna is pointing when
the signal changes from increasing to decreasing.  That is what determines the direction to the
signal.
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PA3BNX
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Posts: 18




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« Reply #2 on: February 28, 2012, 01:39:13 PM »

Hello All,

I am the writer of the software on PI4WAG

The calibration simply sets an offset to the bearing.

So normally you send a signal about 100 metres North or in front of the car

Then you adjust the calibration slider to read North.

You can do this automatically when you press the Call button
in SoundDoppler.exe if the transmitter is sending.
The call button tries to set it automatically to North.

Then you check if the rotation is right so move the transmitter to left and right and see
if the direction pelorus is following to the right side.
If not switch 0/180 to correct it.

That's all to calibrate the Doppler.

I am still working on the software it gets better and better.

In Version SoundDoppler120aAll.zip I did improve the

zerocross detector.

In the low sampling mode (8000 samples a second) it works
better.

The hardware does not change much any more I think.

Of cource you can build and design better hardware
for the SoundDoppler.

73's

Lodewijk
PA3BNX




 
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M0ATZ
Member

Posts: 15




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« Reply #3 on: February 28, 2012, 11:59:23 PM »

Hi both thank you for the replies, very useful.

Lodewijk - the software is excellent, very impressive - i would love to see the vb files!!!!

Thank you for explaining the calibration, that confirmed my understanding. we did some tests on the kit and think we have a working model, doing further tests tonight which should be fun.

Thanks again and well done!!

73

Colin
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PA3BNX
Member

Posts: 18




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« Reply #4 on: March 06, 2012, 01:08:57 PM »

Hello Every Body,


I have the kml routines working now in SoundDoppler.exe

kml  KeyHoleMArkupLanguage.


So you can easy view in Google_Earth now.

I also did made the waterfall spectrum in 64 bar's now

so 360/64=5.625 degrees

It was before just 32 bar's

so 360/32=11.25 degrees

I also made freeze button on the SCF Scoop and the Waterfall screen.

Also I wrote an update in the zero-crossdetector routine.

It's even at just 8000 samples/sec  quite good.

Because I interpollate between the two samples that crosses the zero
and than calc the average between those two samples with the aid of the
amplitude stored in it.


Also I dropped the Zoom function in MyMapping.exe
MyMapping is a program that shows UI-View32 Maps
specially written for RDF (Radio Direction Finders)

(It's included in SoundDoppler.zip file on PI4WAG)

And now I am working on a AutoTrackMAp function that
automatically shows the smallest map where the latest bearing is.

Of course there comes a button in the program that just does one AutoTrack.

So I let you know when it's there
to download.

Happy Hunting Monitoring
« Last Edit: March 06, 2012, 01:18:13 PM by PA3BNX » Logged
PA3BNX
Member

Posts: 18




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« Reply #5 on: March 18, 2012, 12:25:45 PM »

Hello Every Body,


I have an updated version on the site of PI4WAG

with MyMapping131 That has AutoMapTrack

and scrolling with mouse wheel or pg Up pg Dn keys

for scrolling through all the maps in the Map dir.

witch contain the last bearing on it.

All in the zip file SoundDoppler120dAll.zip

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PA3BNX
Member

Posts: 18




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« Reply #6 on: April 17, 2012, 11:53:39 AM »

Hello Every Body,


I have been experimenting with my 4 x 1/2 wave doppler dipole antennas
for the Super Simple Sound Doppler.


I have found that you must use open halve wave dipoles for 2 meter

and then place an extra series diode in series with the coax shield at the dipole feed
point.

So no halve wave dipoles with a gamma match !

So the dipole halve + coax cannot become close to 1/2 wave length witch will be resonant
en disturbing the local field between the 4 dipoles by taking current from the field.

Also use a PVC or wood pole to mount the cross arms as far as they are in between the under sides of the
4 dipoles.

I did put at regular distances around the coax and control cable ferrite clamps
to make sure the cables do not take current from the field near the dipoles.

Make sure you never have resonant elements near the antennas.


Take also a look at the new DDF007 from R&S

http://www2.rohde-schwarz.com/en/products/radiomonitoring/direction_finder/DDF007-%7C-Side_View-%7C-32-%7C-7349.html
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M0ATZ
Member

Posts: 15




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« Reply #7 on: April 27, 2012, 02:43:01 AM »

Great updates thanks for the info, certainly having fun testing the system. weirdly getting some spurious noise when using older laptop for the sound input, do you think this is to do with screening in older laptops or maybe something else?

73

De m0atz
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PA3BNX
Member

Posts: 18




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« Reply #8 on: May 02, 2012, 11:30:48 AM »

Hello,


Eh yes noise is possible from laptop to Vhf RX.

Of course displaying SCF and or XY input screens takes some CPU time
Maybe to much for a 100MHz Pentium 1 laptop.
Also logging in wave file the audio takes some CPU time.


Some soundcards have annoying errors
that they switch left and right channel at unwanted times.
You could then try to click on the label
next to the DCD checkbox with the changing
number.

It will turn very short yellow.

At that very moment the soundcard pointer is reset.


Certainly if you run Win98se and use SoundDoppler.exe

I have it running here on Win98se  old P166 Pentium laptop hi...

But it runs much better on my Dual Core 2. 4GHz with Win XP of course.

But mobile in the car the old laptop is okay hi...
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M0ATZ
Member

Posts: 15




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« Reply #9 on: May 20, 2012, 09:48:37 AM »

ok, fine business, I've got one or two more laptops to try out, I think its old and maybe needs upgrading hi hi.

other than that the system seems to work great stuff, we're out testing again next week with some updates expected!

thanks again, 73
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M0ATZ
Member

Posts: 15




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« Reply #10 on: June 26, 2012, 05:23:58 AM »

Hi Lodewijk- quick one, what software did you use to create the PCB artwork?

Cheers, 73
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PA3BNX
Member

Posts: 18




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« Reply #11 on: June 28, 2012, 12:01:50 PM »

Hello Every Body.


The Matrix PCB work is done in Paint hi.

So just bmp's


I am working to improve the software.

Soon I will release SoundDoppler122 and MyMapping135.exe

on the site of PI4WAG.

I did also make a new design instead the 4013 4001 circuit

almost the same but only with one cheap cd4017 hi..

Take a look on this sites to.

http://members.chello.nl/~w.hofman/pa8w/dopplerRDF.htm

http://www.eevblog.com/forum/projects-designs-and-technical-stuff/radio-direction-finding/


http://www.youtube.com/watch?v=73_M_59gNvc&feature=plcp

http://wiki.spench.net/wiki/SDRDF

73's

« Last Edit: June 28, 2012, 12:08:51 PM by PA3BNX » Logged
M0ATZ
Member

Posts: 15




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« Reply #12 on: June 29, 2012, 02:42:14 AM »

Brilliant, keep up the good work, I've been reading these posts with great interest now. This is such a fun project. I'll make the 4017 switcher and compare the difference with the 4013 / 4001. Nice work.

FB on the use of MS Paint - keep it simple!!

Cheers, 73

M0ATZ
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M0ATZ
Member

Posts: 15




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« Reply #13 on: June 29, 2012, 06:29:51 AM »

Another quick point - do you have any PCB artwork for the 4017 circuit? Many thanks, 73
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PA3BNX
Member

Posts: 18




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« Reply #14 on: June 30, 2012, 10:45:24 AM »

Hello,

No unfortunately I have not done
a 4017 PCB Paint Artwork hi..

So if somebody is wanting to make a new PCB Layout file !

Both units run cool

So the 4013 and 4001 runs okay

But the 4017 runs also okay.

The 4017 has an advantage.

You can very easy be modified to to 3 to 10 antenna's

Just put the reset line from the 4017 to the last antenna + 1 digit.

And adjust the multivib frequency.

The multivib frequency must not be changed

if you switch between 3,4 or 5 antenna's

Because it's all in range.

The SoundDoppler software runs with Doppler frequencies from 300 to 2700Hz or so.

Other wise change the 2 capacitors

in 10nF, 12nF, 15nF or maybe 18nF in the bc547 multivib

But now it should be easy to make a 3 monopoles Doppler to hi
or a 5 monopoles Doppler antenna.

I did build mine on hole Matrix PCB.

And it works okay.
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