Even a functioning HF dipole can be improved
The use of modern technologies has a future in our amateur radio hobby. When some time ago I lost one arm of a really good broadband dipole on KV due to an administrative intervention by the municipal authority, I had to solve our usual dilemma - what and where to stretch or build and how it will work. While searching through many sources of information, I came across a flyer in my own ham-shack, which I took by chance at a stand last year at a meeting in Holice. I almost couldn't believe my eyes, when I saw the device on the flyer, which should be able to accommodate dipoles from 2 x 6 after 2 x 40 m on any KV band. The device marked SYMMETRICAL ANTENNA SYSTEM – REMOTE CONTROL UNIT – AG-3CU promised unsuspected things in its description. After ordering from the relevant company, I was still thinking of some version of the dipole and ended up stretching a single-wire dipole 2 x 19,8 m. Center at a height of approx 15 m on the ridge of the roof and the ends inverted to approx 8 m on the masts seemed quite acceptable to me.
Balun FRITZEL 1 : 1 to the center of the antenna and 26 m of coaxial cable were supposed to demonstrate what it can do. There is only one new in the program itself, nothing power. On 3,5 MHz PSV 1,5 a-N-A 10,1 MHz PSV 2. It was even worse on other bands.
After installing the AG-3CU instead of the FRITZEL balun, things happened. Antenna like that, how stretched it is, can be used on all bands from 1,8 do 28 MHz tune to PSV 1,3 to 1,5.
The control unit located in the ham shack adjusts the antenna to the best PSV after the multicore cable and stores the settings in its memory. After switching the transceiver and the control unit to the appropriate band, the output remote-controlled butterfly capacitor is fine-tuned according to the PSV meter, connected directly to the dipole conductors, in the min. PSV. By simply turning off the power, the output from the input balun is connected directly to the dipole. A pleasant detail is also the common grounding of both arms of the dipole through high-ohm resistors to the ground terminal.
This article is definitely not intended to be an advertisement for a product for that reason alone, that its price is definitely not popular and resembles e.g. the price of the Titan antenna. Even that is rather unpleasant, that the outdoor unit has a control cable fixed in it and this cable is terminated with a multi-pin plug, which is not easy to pull through various spaces for cables. However, a big attraction for the next period is the possibility of constructing a rudder for all KV bands with arms made of fishing rods 2 x 6 m.
Jirka, OK1FTJ
