Radio Direction Finding Technology
is PA8W and how can I contact him?
Before you reach out to me, please read the
First of all, I am a very busy man, and I am doing this Rsdio Direction
purely as a hobby, for pleasure.
Therefore it is important that you absorp as much information as you
can from this website before you email me.
Because yes, silly questions do exist, when the desired
right under your nose :)
Some key understanding:
1, RDF41/42/43 are no receivers, they are RDF processors,
so you will need a separate receiver and an antenna array for the
desired frequency band.
If this is new to you there's a lot of reading to do on this
2, I will not share schematics or firmware other than offered on this
3, I am willing to help students but I am not willing to build your
You will have to do that yourselves with or without my help.
So if you have any sane questions or suggestions feel free to email me:
Who is PA8W (Wil)?
About the above photo:
No, I am not a lucky b... who's operating old radios from an airborne
This photo was taken in the Imperial War Museum in Duxford England,
where they have a lovely collection of old radio equipment.
In one corner, this copy of the Lancaster's radio room is available for
taking a nice picture...
I was born in 1957 in the Netherlands, and as soon as my parents let me
hold the soldering iron, I was connecting batteries, lamps and switches.
A little later, I was building small cigarette-box FM-transmitters
using the OC171, and building basic receivers, audio amplifiers etc.
Ok, I admit, things got out of hand later when I disrupted the
reception of a live soccer game on television for my entire
And I didn't make friends testing my drive-in loudspeakers again and
again in our garage, shaking the neighbours tools from his wallboard...
I did manage to turn my hobby into my profession,
I did turn my profession into my own specialized pro-audio company in
1994, making a more than decent living and enjoying every minute of it.
So mothers and fathers, don't get desperate if your son or daughter
trips your home's mains fuse.
Just keep your flashlight within range and keep in mind that this son
or daughter may one day fix your electric wheelchair or get your
computer virus free and running again...
When I started hamming in 2009, my first goal was to make worldwide
QSO's on HF in SSB.
Due to the small space available for antennas,
I had to find small but effective antenna solutions and because of my
professional interest in audio and intelligibility,
I focused on optimizing my audio to make my station sound "big".
"Your power is in your Audio" is what was reported to me lots of times.
As a minimalist, I get great satisfaction out of tweaking and
optimizing a basic setup.
QRV on 10m, 15m, 20m, 17m, 40m, and on 80m, I worked more than 100 DXCC
entities and more than 35 North American states in my first 6 months of
hamming in 2009,
all in SSB. Not a bad result for 100W and small antennas I guess.
From 2012 on I focused on Radio Direction Finding technology.
Starting off with a classic design (WA2EBY doppler) I discovered that
it had some serious drawbacks.
So first I got rid of the primitive hard antenna commutation, improved
the switched capacitor filter, redesigned the phase-comparator, doubled
the pelorus resolution twice, added specific functions, etc.etc.
After that I turned to a microcontroller to further enhance performance
and user interface.
RDF40, RDF41, RDF42 and RDF43 are the result, plus an
program (MapApp), to present the bearings of multiple stations on a
for easy triangulation.
picture shows some of the approx. 135 meteorological radiosondes
I recovered in the process of testing my radio direction finders.
September 9, 2018 : Winner of the Dutch National
Teams # 2 and 3 were also using PA8W design dopplers!
After participating in the Dutch annual Balloonfoxhunt for a few years,
sometimes finishing as #3,
this time me and my friend PA0TGA using the RDF40 and RDF42 doppler
RDF's were the first team to get to the balloon transmitter.
With a fixed RDF42 at my home QTH and my good old RDF40 in the car, and
RDF-Mapper running on a laptop to show both bearing lines plus our own
we were able to stay right underneath the balloon for most of the 3,5
hours long flight.
The initial challenge of this Balloonfoxhunt is to first pinpoint the
secret launch spot.
Once that is secured, some track predictions give us an indication
where to go to intercept the balloon.
In this case we drove up north to Apeldoorn, where we were a little
behind, and we proceeded east following the balloon until we were right
This way we had to stop a few times to let the balloon pass by and so
after quite some time we were a little over the German border waiting
for the balloon to burst.
After the burst we had to speed up to 150kmh to stay close and managed
to be at about 2km distance when we heard the transmitter land at the
other side of a small river.
7 minutes later we were at the landing spot in the woods.
53 teams arrived there in total, over a time span of about an hour,
which is the largest number since the Balloonfoxhunt started 40 years
My appreciation and thanks go to the organizers of the Balloonfoxhunt,
to Jonathan Musther who wrote this magnificent RDF-Mapper for me,
to Patrick PD2PC who provided me a pretty good second bearing from
Assen with the help of a friend,
and of course to Tonnie PA0TGA my team mate.
My country: The Netherlands!
First, there's some explaining to do here:
Netherlands, Holland, and the Dutch people.
Ok, how do I explain this chaos...
Officially, our country is called the Netherlands.
But most people call it Holland. (simpler to pronounce)
In fact North Holland and South Holland are two of the twelve provinces
in the Netherlands.
So, like England in Great Britain, Holland is no more and no less than
a part of the Netherlands.
And now the hard part, the Dutch...
Well, the people living in the Netherlands are called the Dutch.
And we speak the Dutch language = Netherlands language.
This doesn't sound logical but I'll try to explain:
A long time ago, before there were countries and borders, this area of
Europe was mainly dominated by German tribes.
(you folks still call our easter neighbours the Germans...)
Later on, out of the German dialects, a common language evolved, the
The word Diets evolved to "Dutch" and "Deutsch". (Deutschland-Dietsland)
But right now, the Dutch are the Netherlands, and the Deutsch are the
Did you loose track? Me too...
Whatever, Netherlands, Holland, and the Dutch are the same 17 million
This photo really pictures the history, present and future of the
Netherlands; always battling the waters!
Ever since the 14th century, the Dutch (=Netherlands) people tried to
secure their wet lands by building dikes.
1400 years before that, a great Roman conquerer wrote home that in
Terra Inferior (low-lands) he encountered a tribe of people that had to
be extremely crazy and stubborn to stay in their swampy land,
in spite of the constant threat of water from the sea and two big
rivers, destroying crops and taking lives.
Nowadays, the Dutch have established a worldwide reputation in water
In 1953, the last big disaster struck.
High winds and high tide swept up the waves to unprecedented levels,
damaging and breaking numerous dikes.
Big parts of the coastline were flooded in one night and many, many
lives were lost.
This disaster triggered a great initiative, the "Delta Works";
a number of impressive projects to strengthen the sea defences.
Now, expecting a rise of the sea level in the near future, the Dutch
have to face a new challenge.
The determination and ingenuity of the Dutch will have to provide the
nice examples of big projects that have to protect the Dutch coast from
the dangers of the North Sea.
So please visit the Netherlands (Holland) if you can, and buy some nice
wooden shoes as a trophy and take pictures of the old wind mills.
Or buy a "smoke" in Amsterdam and gaze at our tulips.
We on our turn will make sure you will keep your feet dry during your
Even if you decide to land on and fly off from a piece of the
Netherlands that's several meters below sea level,
Greetings from the Netherlands,