I am a BCB DXer phasing a pair of terminated, untuned pennant antennas. The characteristic impedance of ea antenna is ≈ 940Ωs. 75Ω coax is coupled to ea antenna via 12.5:1 isolation xfmr (≈ 88:7 turns) built with stacked (Amidon) FT240-61 cores. Ea coax then goes to a preamp powered from the feedline. Lately I have been wondering how much signal loss there is across those transformers because of the number of turns involved. I understand that a higer μ core would reduce the turns but they all have higher core losses. Higher μ= higher loss!
How can I eliminate the transformers and feed the antenna directly I asked myself? From what I have read single ended and differential jfet amps are often used with loop antenns. Whereas the jfet has an extremely high Zin the amps can be easily set to match the antenna characteristic impedance. The amp then can be isolated from the feedline via a simple 1:1 iso xfmr or a choke balun. The dilemma I face is how to supply DC power to the amp while still maintaining ground independance?
Thoughts?
How can I eliminate the transformers and feed the antenna directly I asked myself? From what I have read single ended and differential jfet amps are often used with loop antenns. Whereas the jfet has an extremely high Zin the amps can be easily set to match the antenna characteristic impedance. The amp then can be isolated from the feedline via a simple 1:1 iso xfmr or a choke balun. The dilemma I face is how to supply DC power to the amp while still maintaining ground independance?
Thoughts?
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