I am thinking loud about problem presented in my last post above.........
The tiny 1/2 wavelength dipole & pepsi-can sleeve dipole (which is also a 1/2 wavelength dipole) have an inherent impedance of 75 ohms, if both limbs are cut exactly 1/4 wavelength (69mm). This is easy to accurately achieve. Hence the prototype built by DIY, will have SWR very close to 1.
In the Franklin & 5/8 coil tuned antennas, the impedance is brought down to 75 ohms by stubs & coils. These are very sensative to accuracy, and a DIY built prototype will rarely have SWR close to designed SWR.
As a result of above, the1/2 dipoles perform better than franklin & 5/8 coil tuned antennas when used without Amplifier.
When used with Amplifier, the low SWR is compensated by the Amplifier, hence the stub & coil tuned antennas, which have gain of order of 6 dBi or mre, give better performance than 1/2 wavelength dipoles which have gain of order of 2.2 dBi.
The tiny 1/2 wavelength dipole & pepsi-can sleeve dipole (which is also a 1/2 wavelength dipole) have an inherent impedance of 75 ohms, if both limbs are cut exactly 1/4 wavelength (69mm). This is easy to accurately achieve. Hence the prototype built by DIY, will have SWR very close to 1.
In the Franklin & 5/8 coil tuned antennas, the impedance is brought down to 75 ohms by stubs & coils. These are very sensative to accuracy, and a DIY built prototype will rarely have SWR close to designed SWR.
As a result of above, the1/2 dipoles perform better than franklin & 5/8 coil tuned antennas when used without Amplifier.
When used with Amplifier, the low SWR is compensated by the Amplifier, hence the stub & coil tuned antennas, which have gain of order of 6 dBi or mre, give better performance than 1/2 wavelength dipoles which have gain of order of 2.2 dBi.
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