Antena HWEF - cewka



Przecież w tym linku masz wszystko wyjaśnione odnośnie różnych sposobów zasilania tej anteny.
O budowie transformatora na rzeniu toroidalnym opowiada ten fragment:

Commercially-built multi-band end-feds (e.g., ref. 2A/B) use toroidal ferrite cores, such as the FT140-43 and FT240-43. These cores have an outside diameter of 1.40 and 2.40 inch respectively, and are made of material type nr. "43" (a nickel-zinc mix). However, the smaller one (FT140) has a slightly lower AL value ( inductance in μ,H per 1000 turns) than the larger one: 885 vs. 1075. Other companies use a toroidal iron-powder core (e.g., a T80-2 in ref. 1 (for QRP), and a T130-2 in ref. 2C).

Clearly, such transformers are not truly wide-band, covering 3.5 - 30 MHz (80-10 mtrs). If one prefers the lower bands (80/40), then a ferrite transformer with N = 3 on an FT240-43 core (larger AL value) would probably be best. Conversely, N = 2 on an FT140-43 core, would be more suitable when concentrating on the higher bands (40-10 mtr). With this smaller core, 50-60 watt continuous should be OK. The larger core should be OK for at least twice that.

Wind the transformer with enameled copper wire ("CuL", "magnetic wire") with a diameter of 0.8 - 1 mm (AWG # 18 - 20).
Note that when winding the transformer, each time you pass the wire through the core (i.e., including the first time!), counts as one turn. See the numbers in the photo below. The wire of the secondary winding is twisted onto the first turns of the primary winding, to get tighter coupling. The split-winding of the primary side (transition turn nr. 8 in the photo below) is supposed to reduce parasitic capacitance.
Enameled wire is never perfectly coated with enamel, and the enamel does not provide high voltage insulation. Consider using teflon coated wire.
Note that iron powder cores such as the T-200-2 have an AL that is 10-20% bigger than that of the above ferrite cores: 120 μ,H / 100 turns (be careful: AL of iron powder cores is specified as inductance per 100 turns, but for ferrite cores it is inductance per 1000 turns!). However, the permeability of the ferrite core is about 80x larger than that of the iron powder core! Stick with the ferrite cores for this application.



  PRZEJDŹ NA FORUM