Table of Contents
How efficient is a doublet antenna?
An efficient doublet should be at least 1/4λ to 1/3λ at the lowest operating frequency. A 3/8λ version has an efficiency greater than 98% relative to a λ/2 dipole and can have SWR values that are reasonably easy to match.
How long should a doublet antenna be?
The Antenna: The antenna proper consists of a length of copper or copperweld wire, with a center feedpoint. Three popular lengths for the antenna are these: a. 130-140′ (best, if you have the room and want the strongest results on 80 meters.
Does a doublet need a balun?
So yes, unless you purchase an actual balanced line tuner you really do need some balun in the system. – The balun is NOT matching the tuner to the characteristic impedance of the balanced feed line (e.g. 300 ohms, 450 ohms, 600 ohms).
What do you do with an excess ladder line?
Use a sting and tie the excess about mid length of the excess to a higher point that will lift the low arcs about a foot or two off the ground. Throwing in one twist every three or four feet is not a bad idea either as it helps mitigate longitudal imbalance when you run the ladder line close to walls and other objects.
How do you feed a doublet antenna?
The key to the doublet antenna is the form of feeder used. Open wire or balanced feeders are able to operate as part of the actual antenna itself, not just feeding the power from an unbalanced source. The balanced feeder or open wire feeder is able to operate with standing waves along its length.
What is a 9 1 balun used for?
These are sometimes known as a Magnetic Longwire Balun. Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50Ω (unbalanced) coaxial input, hence UnUn.
How does a doublet antenna work?
The doublet antenna is a form of dipole that uses a balanced feeder, often open wire feeder and an antenna tuning unit. As open wire feeder is able to operate with levels of standing waves and effectively becomes part of the antenna, it is able to operate over a wide band of frequencies.
How tall is an 88 foot dipole antenna?
88 foot dipole antenna and other short limited space dipole antennas An analysis of the Cebik dipole and other small limited space dipoles fed with open wire ladder line. Short dipoles and problems [ Home ][ Up ] Related page My G5RV page related short dipole link related external G5RV analysis 88 ft or 44 ft Dipole
Is there an all band doublet wire antenna?
The all-band doublet horizontal wire antenna has a history almost as long as amateur radio itself. Despite all the words and diagrams in handbooks over the years, newcomers still send me questions about the antenna. I have collected the questions and boiled them down to 10, all of which have many variations.
How does the length of an antenna affect doublet?
Small variations in antenna wire length will make no difference to doublet performance or to our ability to match the impedance at the shack end of the feedline. We sometimes see radiation patterns for a Yagi antenna change shape as we move from one end of an amateur band to the other.
How big should a multiband dipole antenna be?
The optimum length for a multiband dipole is near 1/2 wl on the LOWEST band, and the optimum open-wire feed line length is any odd multiple of 1/8th wavelength on the lowest band. This means an optimum 80-meter dipole would be about 125ft long, and the feed line would be 25-30ft, 75-90ft, or 125-150ft long.