description
The D2T is a much more modest antenna, designed specifically for the radio amateur who has limited space for antennas. This antenna claims to be able to operate over the frequency range 1.5 to 200MHz with an average SWR of around 1.6:1 and has gain and directivity in the upper HF bands - it appears almost too good to be true. The specification is given in Table 1.
The construction of the D2T is different from any other mini-beam that you will have seen. It comprises two equal 6m-long elements spaced 2m apart. The first element is fed from the transceiver feed line via an RF transformer / balun. The second element is fed from the first via two metres of transposed open wire feeder, similar to the ZL Special antenna.
The second element has an 820 ohm non-inductive terminating resistor as shown in Fig 1. Each of the wire folded elements is supported on glass fibre tapered rods.

construction
The antenna kit, comprising fibre-glass tubes, an aluminium boom, the terminating resistor and the balun / transformer are shown in the photo. All the other parts, including all the nuts and bolts are enclosed in polythene bags carefully labelled with 13-digit part numbers.
The assembly instructions are very detailed and there were no problems encountered in the construction of this antenna. There is also a detailed drawing, with details of the positioning of every nut and bolt. In addition there are a number of photocopies of close-up photographs of different parts of the antenna, which are very useful if you find the detailed descriptions a bit confusing.
The tools required to construct this antenna include a range of spanners, a small screwdriver, a soldering iron and a drill. This last item is used to drill a hole in the aluminium boom to match holes in the fibre-glass element support clamps once the fibre-glass element supports have been accurately aligned. A nut and bolt is inserted into this hole to prevent the elements being moved in high winds.
The multi-stranded copper wire comes in one roll (part number 6002704000 046) and has to be cut into four pieces "exactly equal to 6.2m" and two pieces "exactly equal to 2m". I was concerned about my ability to cut lengths of wire "exactly" to a given length but overcame the problem by making a wire jig on the drive in front of the house using bricks. The secret is to measure twice and cut once. The ends of the wire are either soldered to lugs, to connect to the transformer or the terminating resistor, or to connecting tubes to connect to the phasing lines.
The wire elements are fixed to the fibre-glass elements using plastic tie-wraps . Once the antenna is assembled, that's it! No adjustments or tuning are required.

installing
The complete antenna weighs 8.5kg (19lb) and was fixed on a rotator on the chimney of the house without difficulty, and without any additional help. From previous antenna tests I knew that this is not an ideal location, due to nearby telephone wires and the close proximity of electrical wiring and plumbing inside the house. On the other hand it would probably be typical of the sort of locations a compromise antenna such as this would be used.
I had no difficulty installing the antenna. I used a different mast-to-boom clamp, using U-bolts, rather than using the one provided. The reason for this was that the original clamp uses heavy-duty bolts with locking nuts that would have to be tightened using two big spanners while, at the same time, supporting the antenna.

how does it work ?
This antenna is such a different concept in multiband minibeams that i tried to make a computer simulation of this antenna using EZNEC.
The simulation performance was similar to the real antenna but exhibited F/B patterns that were worse than the real antenna. The F/B on one band could be improved by placing a small capacitor in parallel with the load resistor but that upset the F/B on other bands. If I had tried to model this antenna before I built it I would have concluded (incorrectly) that the antenna configuration was unsuitable for broadband applications. There many be some who would question the wisdom of placing a resistor in an antenna configuration to tame the wild excursions of impedance that normally occur in a multiband antenna without traps. They might conclude that it is lossy and not worth considering for amateur applications. Yet one of the most effective antennas I know is the non-resonant rhombic - which uses a terminating resistor. The important thing to remember is that the D2T antenna is a high impedance antenna, so all other losses are small. If you consider the case of a small trapped mini-beam the radiation resistance is very low. For a given effective radiated power the current through the elements must be very high. This means that the resistance of the material used to make up the elements is significant : in effect with a low impedance antenna you have a built-in series resistor in the elements. The D2T is an ideal antenna for someone who has a restricted size location and has to install an antenna that does not require adjustment. My experience of installing other mini-beams is that the adjustments are very critical and they can only be tuned for the SSB or CW sections of the band but not both. The D2T antenna has no such restrictions.
The fact that the antenna will work on the lower HF bands - even though its performance is less than a resonant dipole - is also a very positive feature. Thanks to Giovannini Elettromeccanica , Via e Mattei 9, 50039 Vicchio ( Florence), Italy; tel: +39 055 844124; fax: + 39 055 8448797, for making the antenna available for testing. The D2T antenna is featured in the Giovannini Elettromeccanica internet page at http://www.antenna.it and their e-mail address is: giovannini@antenna.it. In the UK, the D2T will be available from Waters&Stanton PLC at £ 395 inc VAT. Writo to 22 Main Road, Hockley, Essex SS5 4QS; tel: 01702 206835, or e-mail: sales@wsplc.demon.co.uk for details.

further reading
[1] The Antenna Experimenter's Guide by Peter Dodd, G3LDO. Available from Radio Today sales, price £15.00 - for details of how to order see Book Browser on pages 60 / 61.