03-23-2020, 08:29 PM
Fact is: That antenna to be most efficient must be resonant. That does not work well for a general coverage receiver. A resonant antenna will have a specific impedance at the feed point that is or can be made to match common feed line. Matched to a feedline that line is resistant to interference. A matching device at the receiver for the line impedance must also be broadband...
There are commercial receiver antennas that will do this. The issue would be matching at the receiver.
The overall antenna as a system will be noise free all along the feedline but not at the antenna. Noise can still enter there.
FWIR RCA used a design called the spider web antenna. A delta matched dipole that was feed by 72 ohm twisted pair. One such model did not need the heavy center balun (heavy as it was in a porcelain housing). The "normal feed impedance of a dipole is 72 ohm, the feed line can be a pair of 14-18 ga. stranded, insulated wire twisted 1 turn in two inches.
Some 30's - 40's era radios included provision for the balanced antenna. Ready for such a feedline. The Delta system has several extended legs that assist in managing the shortwave bands. For BC overall, the antenna serves as loading and the feedline does some reception if one leg is connected to ground.
IMHO the use of baluns for BC will introduce loss and unexpected resonances. I think a more than adequate BC/shortwave antenna is an easy afternoon project costing only for the wire & insulators.
Do not neglect the lightning protection, can be homemade.
YMMV
Chas
There are commercial receiver antennas that will do this. The issue would be matching at the receiver.
The overall antenna as a system will be noise free all along the feedline but not at the antenna. Noise can still enter there.
FWIR RCA used a design called the spider web antenna. A delta matched dipole that was feed by 72 ohm twisted pair. One such model did not need the heavy center balun (heavy as it was in a porcelain housing). The "normal feed impedance of a dipole is 72 ohm, the feed line can be a pair of 14-18 ga. stranded, insulated wire twisted 1 turn in two inches.
Some 30's - 40's era radios included provision for the balanced antenna. Ready for such a feedline. The Delta system has several extended legs that assist in managing the shortwave bands. For BC overall, the antenna serves as loading and the feedline does some reception if one leg is connected to ground.
IMHO the use of baluns for BC will introduce loss and unexpected resonances. I think a more than adequate BC/shortwave antenna is an easy afternoon project costing only for the wire & insulators.
Do not neglect the lightning protection, can be homemade.
YMMV
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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