Limited Quantity Blue Edition
Return to basics with a true home brew project, with enclosure made of PCB!
Resonant Fuchs antenna Tuner consists of 1 piece of Tuner KIT as shown on images. Please note the colour (Blue) of this KIT. Tuner KIT does need assembling and soldering. Images show all parts delivered in the KIT and assembled KIT. Assembly manual is avaliable for download at the bottom of this page. Torodial transformer is already prewound so no transformer winding is nessesary.
To use it you connect l/2 long piece of wire to red socket. This Tuner will work on 40, 30 and 20m bands with half lambda long piece of wire.
No counterpoise needed. This tuner is QRP version, max 10W RF allowed.
Description of Resonant Fuchs antenna
The Fuchs antenna has been known for many years. It has been mentioned in the literature [1] and can be seen in Fig. 1.
Figure 1: Fuchs antenna
It's in the shape of an inverted L, the length of the radiating element is l/2 long and it is fed through a resonant circuit. The resonant circuit should have high Q, which especially impacts the coil selected. The higher the Q, the higher the efficiency of the antenna.
The Fuchs antenna has not been used much mostly due to the fact that it has very narrow bandwidth and needs to retuned every few kHz, something most ham operators do not like. But this is actually the advantage of the Fuchs antenna, because when tuning the antenna, the operator can hear an increase in signal volume and must not make a SWR measurement. A narrowly tuned antenna also functions as a preselector.
Another good feature of the Fuchs antenna is that it is easily pulled across trees and its performance does not vary much with respect to distance above ground in contrast to dipole or inverted V antennas which are commonly in use by SOTA operators.
Further, it has reception 1 to 2 S units better on DX than a dipole with less received noise.
Today's commonly known “end fed antennas” that are advertised and sold around the world are implemented with one wideband transformer, which does work. However, due to their design, those antennas do not have all the advantages of the Fuchs antenna, which has very narrow bandwidth.
After several years of testing the Fuchs antenna on base and portable stations, we believe we have found the ultimate portable antenna that works great, is easy to install and the distance from ground does not have huge impact. See more info at [2].
With a help of QRP ATU a single l/2 long wire becomes a very effective portable antenna.
Figure 2: Portable Fuchs antenna QRP Tuners
Final thoughts
The Fuchs antenna has many great features:
1. Due to a high-Q LC circuit, the Fuchs antenna is optimally tuned to 50 Ohms coax and hence has high efficiency
2. Since it is end fed, its installation for portable operation is easy, only a single wire must be installed over a tree in the shape of an inverted L or inverted V
3. Quick “tuning by ear” makes portable operation easy and quick
4. Its inverted L or V installation is impacted very little by height above ground
5. It features a signal 1 to 2 S units better than a dipole
6. Easy to carry. Dimensions: 10x3x2 cm (1 1/2 x 1 1/4 x 1 inch)
7. Low price
In our KIT you will find properly wound transformer, so no winding is needed!
[1] Antennenbuch, Karl Rothammel DM2ABK, Januar 1969
[2] http://www.aa5tb.com/efha_wrk.html
