Trying again the Waller Flag at IV3PRK – part 2
Building details
This antenna has been originated by Doug Waller, NX4D, and highly developed by Jose Carlos, N4IS, who lately settled the “Top-Beam” which sells very performing systems. See this page TOP-BEAM Systems | Quality low band, high performance receiving systems.…. With these products you have for sure a “Ferrari” on Topband!
Nevertheless, both Doug and JC have been very generous in giving me a lot of advice and suggestions for home building my Waller Flag, after having examined all what was wrong in my previous “not performing WF”.
So, at first, I installed a small (12 meters) aluminum tower with the base insulated from ground; then I found, on a surplus store, a cheap rugged fiberglass 60 mm. tube to use as a mast. The boom is a full length of 8,2 meters’ aluminum tube (from an old ten meters yagi), which contains and shields the phasing lines, but is well insulated from the vertical structure of the tower, and from the ground.
By Mouser I bought the small Hammond aluminum and plastic boxes for the transformers, the central combiner and the loads, and prepared as seen below.
These are their details:
Loads: from a bunch of several 2 watts Allen Bradley 1000 and 180 Ohm resistors, I selected two combinations of series-parallel values to get 580 Ohms for L1, the front loop load, and 605 Ohms for L2, the back loop load.
Transformers: 6:1 ratio for T1 and T2, that is 5 turns on the primary and 2 turns on the secondary over a long binocular core (Fair-Rite 2873006802).
Combiner balun: 1:1 ratio, that is 2 turns on the primary and 2 turns on the secondary over a long binocular core (Fair-Rite 2873006802).
Phasing lines: I could not find, at a reasonable price, a small quantity of the suggested Belden Twinax 100 Ohms balanced coax, so I use two lengths of 50 Ohms RG58 cable taped together to get the same impedance line. Their shields are connected together at their ends and to the boom, which acts as a second shield. On the combiner side both lines are wound on a FT240-31 core (Fair-Rite 2631803802) as common mode chokes; 15 turns of double RG58 can fit on this core, for a length of 2,60 meters which must be added to the phasing line. Thus FL1 is 7,20 meters and FL2 is 6,70 meters long to keep the difference of 0,50 m. between them. See phasing line lengths graphs on this page waller-flag-1--design.htm
At the T junction, the resulting impedance is 50 Ohms, but be careful to keep the correct phase and cross the wires “once” to get the necessary 180 degrees phasing between the loops. T3 is a simple 1:1 balun with separate two turns windings on the same 73 elongated binocular core.
This is the drawing of my Waller Flag, with all dimensions in meters:
One of the culprits in my previous attempt was in the loops: half aluminum tubes and half copper wire. Doug and JC recommended to keep the same material and size, so I used normal 1 mm. house wire taped on fiberglass tubes. I bought on internet 8 cheap 5 meters fishing rods, and used the first 3 sections of them, from 29 to 16 mm. diameter.
They are attached on the boom to the old aluminum ten meters yagi plates by means of good plastic Stauffer clamps available in many sizes in specialized hydraulic material stores. Two big ones of them (60 mm. diameter) have been used to clamp the boom to the fiberglass mast; if I knew that, I could had used a normal metallic mast, being well insulated from the boom.
The feed line is a “Messi & Paoloni Ultraflex 7” 50 Ohms double shield coax cable, but a lot of care has been put in the common mode problem. Ten FT240-31 cores have been used as CMC’s on both feed line and rotator control cable, on the antenna, at the tower base, at the house entrance, and in the shack, associated with 1,80-meter ground rods.
At first, I put in a plastic box, at the tower base, also a Norton 10 dB preamplifier, but took it soon out and kept only a KD9SV BF994 x 5 preamplifier in the shack.
See this page on the tests waller-flag-tests.htm
