PA8W Amateur Radio

Wil, PA8W,  E-mail: PA8W@upcmail.nl           
Back

New Mapping Program for Radio Direction Finding

In the summer of 2016 I called for help in order to create a mapping program for RDF work.
A New Zealand wizard helped me out; this genius developed just the right tool for me.

Recently he developed a new version of the RDF mapper that can display plus upload its bearings and at the same time download and display the bearings of multiple remote mobile and fixed stations!



This is how the setup works:

The microprocessor based Doppler RDF (PA8W RDF-41) automatically exports the very best bearings it calculates.
This data is sent over a simple USB cable to a laptop or computer, running the RDF mapper program.
The RDF mapper needs no installation, just throw it somewhere on your computer and execute it.

The program can be downloaded here shortly!


1,  Connect the working RDF41 with its USB output to a USB port of your computer.

2, Run the RDF visualizer program, and click to the settings page, where you select the right serial port and 9600 Baud for the RDF41.

3, Connect a GPS mouse to your computer, and select the right serial port and baud rate.

(Normally a GPS mouse runs at 4800 Baud.)

4, For fixed applications check the SET MANUAL INPUT box and set the heading (or the RDF41's calibration) so that the bearing lines point into the correct direction of a known test signal.

5, For mobile application you simply uncheck the
SET MANUAL INPUT box.
Now the program calculates your driving direction and as soon as you drive faster than the set minimum speed, bearings will be displayed.



Calibration procedure:


Fixed:
Tune to the signal of a known station and turn the calibration knob until the bearing lines on the map cross the location of the transmitter.

Mobile: Let someone transmit a signal (walky talky) and walk away in front of your car.
Now turn the calibration knob of the RDF41 until the bearing line on the RDF41 points forward.
Let you helper return whilst transmitting and fine-tune the bearing.


Some test results on UHF (424MHz) are shown in the below pictures:



The red arrow is me being a mobile RDF station.
Additionally, you see two blue remote stations being downloaded and displayed.
Obviously, the transmitter is likely to be very close or even in the crossing area of all bearing lines.



Here, the mobile is closing in on the transmitter, with the assisting remote stations being about 3 degrees off and the other being spot on.
The black star is the actual location of the tracked transmitter.

Of course the new RDF mapper can also run in multiple lines mode, so that a mobile station can collect a number of bearings which reveil the Transmitters location:




You can see lines emerging from the highway I drove on, and after some time most of them cross the area under the circle, which I added by hand for explaining.
It is obvious that this fully automatic RDF system is a very powerful tool for mobile RDF work.
The driver only has to take a short peek at the screen to know what part of the city he has to address.

Obviously we could do with fewer lines, a lower audio input level into the RDF41 would reduce the number of bearings that would be exported to the RDF mapper.

A big thanks to my friend Jonathan Musther from New Zealand!


73, Wil.


Back