DL6WU Portable Beams
(also known as the Wash Pin Antenna's)
For portable operations (or basically anything outside the shack)
I wanted to have for both 145 and 435MHz a simple but well performing beam.
Also I wanted these antennes to be able to be taken apart very quickly.
Frans, PE1RXJ, started experimenting with designs according to DL6WU with good results. G3SEK has a good webpage with details. Another site with design directions is that of K7MEM . Frans used LEGO bricks to mount the elements on the boom. Using LEGO bricks was especially good as the elements 'clicked' nicely onto the bricks. Below a picture of the 2x 145 and 2x 435Mhz beams of Frans during a fieldday:
On the picture below the mounting of the elements using the LEGO bricks is shown:
However, with the LEGO method it isn't really possible to have the dipol mounted quickly, and therefore I preferred to have another solution. I found that in washpins. The washpins are kept in place on the boom with pieces of rubber (cut from a used innertube of a bicycle):
The washpin method allows fast assembly of the whole antenna within 30 seconds. Compared to the LEGO method that is a plus. But the LEGO method as such is mechanically much more stable. So depending on application either the washpins or the LEGO bricks win.
We used a simple T-match:
The connecting pieces are made by sawing small blocks aluminium, drilling first two holes, then the third hole, and finally saw the piece into two small pieces. Details are provided in the next two pictures:
A detailed view of the 435MHz balun is depicted below:
DL6WU antenna for 435MHz:
These are the sizes (mm2) used for the 435.0MHz beam:
Calculated gain: 9.79dB
These are the sizes (mm2) used for the 145.5MHz beam:
Calculated gain: 6.46dB
All elements are made of aluminium with 5mm diameter.
All elements mounted isolated from the boom, distance element/boom: 8mm (not critical)
With these 2 antennas AO51 can be operated "noise-free" (145up/435down) using a 5W tranceiver (eg THD7).