The G5RV Antenna ; It is an antenna for radio amateur use for all bands between 80m and 10m . It consists of a 31m long Multiband HF Dipole that has a ‘ladder’ cable feed of 450 ohms impedance is 9.50m long. At the end of the parallel ladder cable, a 50 ohm coaxial line can be placed (requires balun).
Summary
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- 1 Story
- 2 Features
- 3 Construction
- 4 Sources
History
These types of antennas were already well known in the 1930s in the United States . In December of 1935 in the journal Signal Collins’, Collins Radio Company published an antenna multiband 2, 3 or 4 bands (depending on configuration) tubes using copper as open lines. Again it appeared in the “Radio Antenna Handbook” of the year 1936 . Then it appeared in 1937in the “Johnson Antenna Handbook”. So, to be fair, the correct name for the G5RV and its variants should be “Collins multiband antennas”, or more precisely “Collins version of Zeppelin Antennas powered at the center” (Collins version of the center-fed Zepp) . The antenna that Louis Varney very timidly published in 1958 in an article of only 2 pages in the magazine “RSGB Bulletin”, was titled “An Effective Multi-band Aerial of Simple Construction”. Varney describes the classic dipole there with an irradiator of 102feet (31 meters), 51 feet each arm, and with a 10.36 meter adaptation section of 34 foot parallel open line, or 8.8 meters of 300 ohm tape. That is the real G5RV. But probably today nobody wanted to build that same antenna, since they were looking for an adaptation to 72 ohms (which was what was used at that time), and today they are looking for 50 Ohms. Many of the G5RV antennas are actually “variants” of the classic G5RV, or something similar. The fact that the G5RV was suggested by a radio amateur enthusiast, such as Louis Varney, helped his version of the Collins antenna become popular with radio amateurs .
characteristics
There are two versions of this antenna, the long one and the short version where the latter has the same physical disposition as its older sister, but its dimensions have been cut in half. That is to say, it is formed by a horizontal cable of 15.54 meters, divided into two exactly equal parts (2×7.77 meters) and by a ladder of 5.18 meters.
G5RV antenna short version
- In 3.5 Mhz. The antenna can work mediocre.
- At 7 Mhz. It will work as a half wave dipole.
- At 14 Mhz. It will function as a dipole of two half-waves in phase.
- At 21 Mhz. As a whole, it will be a more ladder antenna that radiates in a double wave, having at its center an impedance of about 90ohms that may be acceptable.
- At 28 Mhz. It will work exactly in three half-waves, this being the most favorable situation and at its center we will have about 75ohms of impedance.
Building
The ladder can be built with two enamelled wires of 1.6 mm diameter stretched and maintained at a distance of 30mm between centers. To keep the separation constant, you can use bars made of plexiglass, nylon or any other material that will be drilled 2 holes of 1.8 mm (to pass the two threads) 30mm apart . The ladder can be replaced by tape television of 300ohms, but for this, it will be necessary to take into account its speed coefficient, which is usually between 0.70 and 0.85, depending on its quality, so that the resulting length can range between 4.57 and 4.75 m. The use of an antenna coupler is recommended, along with the equipment, to correct any minor maladjustments that may arise.