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Radio Direction Finding
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PA3BNX:
Hello Every Body,

Nice to watch this TDOA with Arduino

2015 Anatoly Kuzmenko.
 
https://youtu.be/eoOY659YMXo
http://coolarduino.blogspot.ca/
I7SWX:
Hi Lodewijk,

I have started your direction finder project, basically similar to the 4013 & 4001. In place of the 4001 I have used a 4011, driving four transistors to drive the antennas diodes switching. This gives the same switching functionality.

Sorry if the following questions have been reported and answered in the discussion but I did a quick reading of some notes but I could not see anything.

I have some questions please:

1) Your 4001 solution defines, from top to the bottom, outputs antenna #4. #3. #2 and #1, mine has same selection. The solution with the 4017 gives the antenna selection, top to bottom, #1, #2, #3 and #4.
       a) which is the antenna # that is defined as North ?
       b) is the antennas rotation clockwise or anti clockwise, i.e North, East, South, West or opposite?

2) For the 4001 the clock synchronization is on the #4, while for the 4017 is on the #, right?

3) Which is the loss on VHF between the doppler switched array (using 4x dipoles) and a single fixed dipole connected to a receiver?

4) I have replaced the RFC at the dipoles with a 1:1 balun hoping this would help to reduce hands presence effect on the coax cale to the receiver, but I am not sure how much (if) changed. I will try to put on the dipoles short coax a clip-on ferrite element.

Thanks for your comments and congratulations for your interesting project.

Best 73

Gian
I7SWX
PA3BNX:
Hello Every Body


Tnx's Josh Clough for this link

SDR RTL Dongle experiment wit three GP antenna.

An RTL-SDR Phase Correlative Direction Finder
http://www.rtl-sdr.com/an-rtl-sdr-phase-correlative-direction-finder/

Sources
https://github.com/tejeez/rtl_coherent

Youtube



I7SWX answers

In sounddoppler.exe software you can switch the sequence with CW/CCW 0/180
And correct with the actual bearing with the calibrate bar

Witch antenna is North is not very important you can calibrate 360 degrees

The loss compared dipole to monopole is theoretically 3 dB

With a 1 diode and rfc at a monopole antenna the
Coax shield earth at base of antenna ground plate (very important)
Or magnet feet with lots of capacity to car roof

The 2 diodes and rfc and leak R for dipole A rf 1:1 balun is possible after
the 2 diode and rfc.

Make sure if using dipoles the vertical dipoles have the top part of antenna connected to center conductor coax. (No phase shifts)

4 dipoles works best on stationary mast

On car roof always the 4 monopoles on ground plate.

For 70cm UHF on car roof you could have more monopoles
like 5 or 6 so the aperture is better and then the 4017 circuit is more handy.

On 2 meter VHF 4 antenna on car roof fits best.

If using indoor on a loft or something like that the monopole 4 array
with ground plate works best.

 ^-^

 


I7SWX:
Hi Lodewijk,

thanks for the prompt reply.

I do appreciate your comments.

I have inserted the 1:1 balun as you did report, plus added a clip on ferrite on half dipoles coax cable from feed point to switching point. All antennay array box and support are plastic (external electric conduit and box).

I hope I can have the cable not interacting with the antennas having added the ferrite clipped  on.

I Also I have added a remote RF attenuator into the array, at lowest attenuation I loose 4dB.

I will use the DF on fixed portable installations, not mobile. The support is also PVC.

Yes, I have done the mark to be sure the center cox cable is connected to the top element of dipoles.

I have now a clear understanding of rotation and direction of antennas.

Thanks for the additional info for 70cm use. OK for the 4017 counter use. I found this info after I did assembled the 4011 solution, as I had that IC available.

Best 73

Gian
I7SWX


PA3BNX:
Hello Every Body,

The arduino 1.04 software is ready now with

A potmeter connected to A1 +5V en earth for manual calibrating the lm3914 pelorus and the arduino doppler
without PC with USB.

If no potmeter connected or potmeter totally left or right turned it uses the
Terminal calibration(Mymapping.exe)

Center potmeter is 0 degrees calibration

The arduino with doppler hardware and led pelorus lm3911 draws about 80mA.

So it can easy run a time on a single 9 Volt block battery
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