In the summer of 2016 I called for
help in order to create a mapping program for RDF work.
A New Zealand wizard Jonathan Musther helped me out; this genius
developed just the right tool for me.
he developed a new version of the RDF mapper that can display
upload its bearings and at the same time download and display the
bearings of multiple remote mobile and fixed stations.
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.
RDF mapper needs no installation, just throw it
somewhere on your computer and execute it.
Jonathan offers the program for approx. 23,- euro, with excellent
He also offers to customize it for a very modest price.
few RDF41 radio direction finders, linked together
via Jonathan's RDF Mapper make an affordable but yet extremely
capable radio direction finding system.
to RDF Mapper
Short demonstration video
is how the setup works:
Connect the working RDF41 with its USB
output to a USB port of your computer.
Run the RDF Mapper program, and select the correct serial port
and 9600 Baud for the RDF41.
computer doesn't yet have a USB driver for the CH340 USB controller of
the RDF41 you can download it here:
3, Connect a GPS mouse to your computer, and select the right
serial port and baud rate.
a GPS mouse runs at 4800 Baud.)
the USE MANUAL INPUT box unchecked.
the program calculates your driving direction and as soon as you drive
faster than the set minimum speed,
bearings will be displayed as soon as the RDF41 thinks they are good
enough for display.
For fixed applications no GPS is needed, just check the USE MANUAL
INPUT box and set the
(or the RDF41's calibration) so that the bearing lines point
into the correct direction of a known test signal.
You will have to manually set your location by clicking on the map.
mentioned, the RDF Mapper can upload your bearings and download
bearings from other RDF stations to present them on your screen, using
These options are highly self-explanatory but Jonathan or I will help
you out if you encounter any problem.
if you would like to use your own server Jonathan will offer you all
that's necessary to do so for a very modest price.
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
Obviously, the transmitter is likely to be very close to or even in the
crossing area of all bearing lines.
the mobile is closing in on the transmitter, with the assisting remote
stations one being about 3 degrees off and the other being spot on.
The black star is the actual location of the tracked transmitter.
Just as the previous RDF Visualisation, the new RDF mapper can
also run in multiple lines mode,
a mobile station can collect a number of bearings which reveil the
can see lines emerging from the highway I drove on, and after some time
them cross the area under the circle, which I added by hand for
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.
could do with fewer lines than displayed in this example:
A lower audio input level into the
RDF41 would reduce the number of bearings that would
to the RDF mapper.
think I can safely claim that the RDF41 plus RDF Mapper are much closer
to professional RDF performance than any other kit or amateur design
found on the internet.
Given the soft-commutation of the RDF41 and
therefore its excellent sensitivity, its proven accuracy and smart
suppression of corrupt (multipath) measurements,
given the mapping
and networking options offered by RDF Mapper, I can't think of any
affordable kit or amateur design that comes anywhere close to this.
A big thank you to my friend and genius Jonathan Musther from