The Double Zepp The W3EDP Longwire with MTFT

Feeding the Double Zepp with Baluns

Aperiodic antenna 10-40m Vertical-L Fan-Dipoles

Short aperiodic multiband antenna for 10-40 m

Everyone wants antennas that have a high  effectiveness on as many bands as possible. Unfortunately, this is usually associated with higher electrical and mechanical effort. Especially for portable operation or limited space but also compromise solutions come into question, which are easy to build. The suggestion for such an antenna from HB9KX (sk 2013) will be examined here in more detail.

In the past, the amateur bands had frequency harmonics, which greatly facilitated multi-band operation. In the mneantime the WARC bands have to be added. Commercial services using broadband shortwave spectrum use damping resistors as in the well known T2FD. However, this require an additional balun 1:10. This raises the question of whether things can not be easier.

In the meantime, aperiodic antennas which are  fed with an un-un of the ratio 1: 9 as "Magnetic Balun", have been naturalized. The resulting losses are likely to be in similar areas as those with damping resistors. An additional antenna adapter ("tuner") is usually needed.

Fig. 1: The original scheme of the antenna
Theory of the drawn antenna

The 10.5 m long antenna was described by Kurt Hübner, HB9KX, in [1]. It is shown in picture 1 as original. It is an asymmetrically powered antenna, which is to use the ohmic damping according to the windom principle a well tunable impedance value.

Honestly, I did not understand the principle of drawing. That would be a single wire windom with 100 Ω resistance to the shield of the coaxial cable. There are two sharp resonances at 7.9 and 16 MHz, between the SWV rises to over 10, no trace of broadband. 

Experimentally, the antenna was constructed as shown in Figure 2. The resistor is parallel to the feeding point between the two antenna sections. Maybe HB9KX meant that too. My research for length data with EZNEC show (on the bands except at 21 MHz where the ratios are less favorable) the parallel resistance of 100 Ω brings the impedances with acceptable efficiency close to 50 Ω. With the help of a resistor parallel to the feed point, a SWV is reached, which allows operation without any tuner antennas. The price are losses that can be between 30 and 50%. This only means a drop of the signal by 2-3 dB.

There are several options for the construction: stretched horizontal suspension, built-in as inverted Vee or vertically as a vertical radiator with a 12 m GRP mast. In this case, the lower, shorter section can be led away obliquely downwards even at a 45 ° angle. For this purpose, then a 10-m mast is sufficient as a carrier.
The load resistor should accommodate about 1/3 of the transmit power for CW / SSB operation. For the usual 100 watts of common transceivers, I have used 18 low-inductance metal oxide film resistors with 1
.8 KΩ / 2 watts connected in parallel.
Unfortunately, because of the dissipated heat loss, you cannot place the resistors in a weatherproof box. Unless it succeeds in an open construction that keeps water out. Who wants to use only the basic version, mounted the resistors firmly on the center piece. Thus, the antenna simplicity is probably no longer to beat.

Fig. 3

I made a center piece out of a PE plate (kitchen cutting board), which contains both a PL socket for connecting a coaxial cable and two banana jacks. This is documented in Figure 3 (top of the plate). At these two sockets, the attachable resistance (Figure 4) can be connected from 18 parallel metal oxide film resistors with 1.8 KΩ / 2 Watt or a two-wire cable. To complete, Figure 5 shows the underside and Figure 6 the plate with inserted resistor. This gives you a total of three options:

1. Antenna with 100 Ω parallel resistor and coaxial cable connection

2. Direct connection for coax supply via PL socket without resistors

3. Connection of a two-wire cable ("chicken ladder")

The antenna wire of the pattern antenna is of the type DX-Wire-FL and consists of insulated, hard-drawn copper wires. This is flexible, but very tensile. This can also be a free hanging

The antenna wire of the pattern antenna is of the type DX-Wire-FL [3] and consists of insulated, hard-drawn copper wires. This is flexible, but very tensile. This also allows a freely suspended antenna to be created between two guying points. Whether insulated or uninsulated wire is used is for the intended purpose but absolutely uncritical.

Above Fig.4: The 18x resistors in parallel
Right Fig. 5: Down side of the plate

Fig. 6: The upper side of the plate without the resistors

The practical portable operation as a vertical radiator with a 12 m GRP mast demonstrates the perfect usability of the antenna. Especially at 20 m, the results were surprisingly good, which is probably due to the flatradiation angle. The heating of the resistors (nominal load of 36 watts maximum) in CW or SSB operation shows that they appear not to be overloaded. Conversely, obviously enough RF power> = 50 watts is emitted, which underlines the usefulness of this arrangement. One must consider that with MTFT 1: 9 solutions and mismatch of the coaxial cable also losses occur, in addition, a tuner is needed. This makes the antenna described as a simple solution not unattractive.
Without the load resistor (option 2), resonances at <7, 12.8 and 26.8 MHz with SWV <3 are apparent. This suggests experimenting with the antenna without resistance with built-in ATU. The tuners in the Kenwood TS-590S and Icom IC-7400 are perfectly tuned on the 7 and 28 MHz bands.
It becomes interesting, if one uses option 3 with two-wire line (without resistance). Of course the result depends on the length of the "chicken ladder", in addition you need a Balun 1: 1 or 1: 4 and an antenna tuner.With 9 m Wireman ribbon cable I could with an automatic tuner AT-100 Pro ll using make of such baluns on all bands between 10 and 40 m operation.

It must be pointed out that one should install at the transceiver input in any case a standing wave barrier in the form of a power balun.

The SWV with load resistance between 7 and 30 MHz (Figure 7) shows values ​​<= 1.75, which allow a transceiver without ATU to work on all bands, usually without performance degradation. The graph shows the actual standing wave curve in the feed point, the influence of the connected supply cable type H-155 is already calculated out by the analyzer. At the end of a coax feed cable, the SWV is lower depending on the length



[1] Hübner, Kurt (HB9KX): Einfache Kompromissantenne für 10-40 m, OldMan 1988, H. 10, S. 32-3

[2]: Programm EZNEC+ Ver. 6.0.14 von Roy Lewallen (W7EL), P.O.Box 6658, Beaverton, OR 97007, USA  (e-Mail [email protected]),

[3] Bogner, P. (DK1RP), Technischer Handel – Antennentechnik, Tulpenstraße 10, 95195 Röslau Tel. (09238) 990845,