DL4MEA irradiator
Finding a suitable reflector for a dish with such a focal ratio (f/D 0.4) turned out to be a tough nut to crack. The reflector itself covers part of the mirror, reducing the gain. With a small dish, this effect is quite pronounced with commonly used reflectors. The solution is a reflector according to DL4MEA.
Ožarovač tvorí celovlnná slučka (quad) pred reflektorom s priemerom lamda/2 vo vzdialenosti lambda/8I intentionally do not give dimensions in millimeters, because the irradiator can be calculated for the frequency of need.
Construction of the DL4MEA irradiator
The construction is clear from the pictures. The reflector is a circle made of single-sided cuprextite with handles. A hole is drilled into the reflector for an N-connector (female for the cable). A piece of 50-ohm coaxial protrudes from it, on which the ring of the irradiator made of copper wire (diameter 1.5 mm) is soldered. Bending it into a circle is simple: we mark the required length on the stripped wire and twist it through a tube of a smaller diameter (the wire springs after it is released). We cut off the ring at the mark with pliers and solder it to the coaxial. To increase mechanical stability, we used a support column made of Teflon (the dielectric of the coaxial cable) opposite the connector. The column is screwed to the reflector from the bottom. Finally, we sprayed the irradiator with several layers of colorless varnish.
DL4MEA odporúča nastaviť ožarovač na minimálne PSV (supposedly 1.1 can be achieved) by changing the size of the emitter - reflector. We did not do that, but when comparing the parabola with DL7KM (approx. 7dBd) the satellite dish came out as the clear winner. The covering of the satellite dish by the radiator is also noticeable. When pointing directly, the signal is a little weaker than when the satellite dish is pointed a few degrees away. At approx. 1.5W of power we did QSO na 324km obojstranne za 59. Kto chce lepšie výsledky, môže sa poobzerať po väčšej parabole, platí, že čím väčšia plocha zrkadla, tým väčší zisk.
Literature:
[1] https://www.QSL.net/dl4mea/