Nico ZS4N build the DK3 Screwdriver HF Mobile Antenna

In this article we will be looking at how Nico ZS4N constructed his version of the DK3 Screwdriver HF Mobile Antenna.  I am sure many of you will agree that the construction of this antenna is not for the faint hearted. From the images it is quite clear that Nico ZS4N showed great building skills and craftsmanship in constructing this antenna.

Lets first look at the background of this antenna.  I will also add a few PDF files that explain the construction and performance of this antenna in detail.

Background of the Screwdriver Antenna

• The DK3 Screwdriver antenna was invented by Don Johnson (W6AAQ). The

DK3 is an HF antenna designed for operating on any HF frequency (10m through

80m) WITHOUT leaving the vehicle to change or adjust the antenna.

• The DK3 Screwdriver antenna is adjusted by remote control to give it multi-band

capability. A cordless screwdriver motor (which gives the antenna its name)

housed inside the lower mast unit of the antenna moves the embedded inductance

loading coil up and down. The portion of the coil that remains inside this lower

mast unit is inactive. The exposed portion of the coil provides inductance loading

to compensate for the capacitive reactance associated with short mono-pole

antennas like this one. The adjustable inductance loading allows you to achieve

resonance for a wide range of frequencies.

• The Z-match built into the bottom of the lower mast unit matches the antenna to a

standard 50-ohm coaxial transmission line. This eliminates the need for a tuner.

• Although the DK3 antenna is not plug-and-play, Don Johnson provides good

written instructions and suggestions, and even excellent telephone support to help you

set it up and make it work. 

• Due to its popularity, there are several different versions of the Screwdriver Antenna on the market. Some of the vendors offer improvements over the DK3(such as a plug-and-play version, 160m capability, or a lighter and more portable version of the DK3).

Diagram

DK3 Construction

More information  BIG DK3  By W6AAQ  (PDF Download)

Conclusion

The DK3 is probably the best mobile antenna for hf. It is also well known as the screwdriver antenna. It works on all hf bands (10m-160m) without changing the whip. Well, the DK3 is not really  inconspicuously, but still better than some other hf mobile antennas.

The whole antenna works as a quarter wave radiator. The body of the car is the ground.  There was a screwdriver antenna shootout at the parking lot during the International DX Convention in California (DK3, High-Sierra, Hi-Q, Drill Motor and one other brand). The DK3 took the first place in DX contacts at the convention. Please be aware for the cheep "remakes" of that fantastic antenna. Make sure you build or buy the original DK3 antenna by W6AAQ.

Congratulations Nico ZS4N on building the DK3 Screwdriver HF Mobile Antenna from scratch in your workshop.  

Images:  Click on images for larger view.