Radio Direction Finding PA8W

The content of this website is a copy of a part of PA8W’s  website:
The inhoud van deze website is een kopie van een deel van PA8W’s website.

This website is dedicated to Automatic Radio Direction Finding for radio amateurs and for semi-professional use.
In 2012 I started building and experimenting with Pseudo Dopper Direction Finders and found that in the existing common amateur designs there’s plenty of room for improvement.
So I started doing what I like most: Finding and solving imperfections yet keeping things as simple as possible.
My motto: A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away. (Antoine de Saint-Exupery)

So the initial WA2EBY doppler turned into a PA8W version V1, V2, V2.1, V2.2, V2.3, and the 8-antenna V3. These models were reproduced by radio amateurs all over the planet.
Then I went on to microcontroller based direction finders: RDF40, followed by an 8-antenna RDF80, and the current models RDF41 and RDF42.

Parallel to these developments I found ways to fundamentally improve the necessary doppler antenna arrays,
and developed a very simple Amplitude Array that -in conjunction with an RDF41 or 42- can hunt signals that a pseudo doppler simply can’t cope with.

(Note that I built only two 8-antenna designs, in both I found that the more complex 8 antenna system hardly offers any advantage compared to 4-antenna designs, at least for amateur radio use. A good 4-antenna design performs so well that generally only external factors limit the accuracy if the RDF system.)

For those who would like to build their own Radio Direction Finding system; I will be happy to help out with kits, parts or answers.
Just send me an email.

73, Wil, PA8W, E-mail:

All information and software on this website is freely available for non-commercial use, though entirely at your own risk. Additionally, we can never be held responsible for the content of webpages or files we link to.

Here’s the link to the primary website:

The website of my friend PD0G who created and maintains this website,
who builds very nice Arrays :  or

73, Wil, PA8W, E-mail:

Winner Dutch Balloonfoxhunt 2018

September 9, 2018 : Winner of  the Dutch  National Balloonfoxhunt.
Teams # 2 and 3 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 my 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 position, we were able to stay right below the ballon 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 underneath.
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.

In total 53 teams arrived there, over a time span of about an hour, which is the largest number since the Balloonfoxhunt started 40 years ago.
My appreciation and thanks go to the organizers of the Ballonfoxhunt,
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.