The NYFAZ respectively DL4CS antenna
This designed by me antenna despite of small dimensions is suitable as a receiving and as transmitting antenna. As a radiator and as coupling loop is a normal two-wire speaker line. For such cables, the industrial designation NYFAZ were used to be common in Germany. So I originally gave it the name NYFAZ antenna. But you may also call it gladly DL4CS antenna ;-)
The antenna is a bit more broadband like conventional magnetic antennas of this size. Nevertheless the resonance point is still very pronounced and coincides nearly with the best standing wave ratio. Self-evident the antenna is rather an makeshift antenna for cramped conditions. Still the results achieved with this antenna surprised me very much. Although there is no exact 50-ohm adaptation, the antenna with its two rotary capacitors can easily be matched to 50-ohm transmitter outputs, even with different coaxial cable lengths. It was in all experiments without difficulty a VSWR of better than 1.5 achievable. The tuning process goes in a similar way like a Collins filter.
With a mounting cross of only about 40 x 40cm and two 50pF rotary capacitors, f.e. the antenna is suitable for the 10m band. With an RF power of only about 1 Watt, at a receiver of the Hamburg 10m repeater DF0HHH in about five kilometers away, a almost noise-free signal was achieved. Using a wearer cross of two battens (each 2m in length) were on the 40m-band also reached useful results. In this case, the matching was done with two 500pF rotary capacitors. Despite of sub-roof mounting and with a transmission power of about 100 W was at good propagation conditions from Hamburg, among others, the participation in a SSB round with stations from Switzerland, southern Germany and the North Sea possible. At all participating stations, my transmissions were not particularly powerful, but mostly strong enough. By listening to own test transmissions with various Web SDR receivers, comparable results could be confirmed for different reception locations.
The above photo shows the simple interior structure of a for QRP designed NYFAZ antenna coupler. Without a fixed wearer cross such an antenna, is for example also well suited to use in a hotel room. The loudspeaker cable used can, for example, be fixed to furnishings with shoelaces or clothespins there. Depending on the nature of the substructure, this antenna also simply could be spread horizontally on the floor. Experiments with different loudspeaker cable types and cable cross sections showed that then with the cable lengths something might have to be experimented. Such a NYFAZ wire antenna, that should fit into each luggage, is shown below. It consists of the coupler and radiators for the 40m and 20m band as well as an extension cable with which the 40m radiator can brought into resonance in the 80m band.
For demountable constructions of this antenna the imagination has no limits. There are also many possibilities for fixed constructions. For example, I made an antenna for the 10m band, hidden in a picture frame.
I ask you to refrain from criticism, it be a tunable dummy load. I know that there are better antennas. But there are hardly any antennas that can be produced so easily, with such a cheap material, and with so small dimensions and then deliver even so useable results.