Band antenna 27 MHz
A new range of civil communication 27 MHz gave the opportunity to go on the air to the many thousands of radio Amateurs. But sooner or later the owner of a radio station is becoming a question of increasing the communication range. It may be necessary to communicate with a remote object, for example, a cottage, a place of rest or with friends by the owners of radios on 27 MHz, residing at a considerable distance.
You may fond and distant relationship at 27 MHz, and collecting QSL. In the world hundreds of thousands of people are addicted to this, and QSL card CB-stations, in my opinion, much more beautiful cards of Amateurs.
In any case, the conduct of long-distance communication with the whip antenna, which is attached to the radio, it is impossible. You must have an effective outdoor antenna. But the antenna should more appropriately be attached to the transmitter.
Most imported transmitters SV-relation has a BNC antenna connector that allows you to disconnect the whip antenna and connect the outer (Fig. 1). This transmitter allows you to connect a 50-Ohm coaxial cable, which is loaded on the antenna impedance from 30 to 100 Ohms.
The antenna described in this article, will match these settings. Transceivers SV-relation of production of the CIS and simple foreign radios may not have this connector. In the case of Your transceiver for long-distance communication connector like this you need to install. Further, the output of these transmitters to reconcile it with a 75 or 50 Ohm cable will need a simple matching device shown in Fig. 2.
The inductor used in the matching device is frameless. She wound a copper wire with a diameter of 1-2 mm on the mandrel with a diameter of 2.2 cm and is stretched to a length of 4 cm Number of turns - 10. Cable initially connects to the 2nd round of the coil, and the antenna of the transceiver - by the 4th.
The variable capacitor should be air. The use of ceramic trimmer capacitor leads to the decrease of the efficiency of the device. Structurally, the device can be arranged in the form shown in Fig. 3. Box should be made of metal - copper or foil fiberglass. The joints should be carefully soldered. After setting the box can be closed by the cover, and adjust the condenser again. To configure the matching device can using the signals SV-stations or simple RF voltmeter. Attaching the antenna and the output of the transceiver to different coils of the coil, we achieve maximum deflection of the voltmeter or maximum signal reception.
But to configure matching device, of course, the necessary antenna. Fans of far NE-swaei need to remember antenna for DX must be either high, or long. Usually in cottages or in a private home there are no problems with the installation of the antenna.
It can be a simple half-wave dipole with shoulder length by 2.7 m. For the efficient operation of the dipole must be raised to a height of at least 2.5 metres from the ground. The dipole has a radiation pattern in the form of eight. It can be made of copper, aluminum or steel wire with a diameter of 1-4 mm.
Central lock-easy to do from foil fiberglass, cutting the foil in the middle. Cable or can be directly soldered to the foil, or make it curved, which is better, as in this case, the cable is reliably protected against the ingress of moisture inside.
In any case, the uncovered cable should be protected from moisture with paraffin or epoxy resin.
End insulators can also be performed from thick fiberglass, foiled and non-foiled, but you can just snap dilatory nylon cord or fishing line to the blade antenna.
It is desirable that the cable from the dipole antenna was perpendicular to the blade antenna on at least a length of 2.5 meters. This antenna can be arranged in parallel to the ground, but also vertically, and at an angle thereto.
For the whip antenna (Fig. 4) can be used as an insulator plastic, wood, or, better still, special support insulator. Useful top end of the antenna to stretch with nylon cord to enhance its sustainability. Whip antenna has a circular radiation pattern that in some cases it is convenient. Such antennas can also be installed on the roofs of city apartment buildings.
If You want to contact the place of fishing or hunting, it is desirable to use antenna Beverage (Fig. 5). The antenna should have a length of fabric at least 40 meters (or more) and may be formed from wire of diameter 0.5-1 mm., the Wire can be suspended at a low height above the ground - 1-2 meters. At the end of the load of the antenna and the impedance matching device, it is desirable to use 3-4 of the counterweight.
This antenna can be installed on the roof of a multistory building. Matching device in this case, both the antenna and the transceiver.
With appropriate experience, You can use any complicated Amateur coherent antenna, counting the dimensions for SV-range.
In conclusion, I want to give advice: do not try to amplify the signal of Your CB transceiver. Many CB radio production of the CIS and simple foreign portable transceivers do not allow to obtain high-quality output signal when the gain because the transmitter in them assembled by a simple scheme, where the master oscillator with quartz stabilization operates at a frequency of radio transmission. As a result of insufficient (and sometimes nonexistent) shielding the housing of the radio station in strengthening its RF power signal quality may deteriorate significantly, not to mention television interference.
Better put the power to install more efficient antenna or buy a station industrial manufacturing with a powerful output.
Author: I. Grigorov (UZ3ZK); Publication: krasnodar.online.ru/hamradio, www.cxem.net