Experience in operating a handheld small-sized antenna. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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This article may be useful for those who want to experiment or those who cannot accommodate a full-sized antenna.
In my daily work on the air, I use a small-sized antenna. It is a frame with a perimeter of 4,7 m, made of copper wire (see picture).
At the voltage antinode point, the antenna is electrically extended using a variable capacitor (this method of electrically extending the antenna allows you to increase the efficiency more than other methods). Power was supplied to the antenna from the middle of the vertical side with a RK-50 cable (RK-75 was also tested, the antenna works no worse than with a 50 Ohm cable) through a simple balancing device. Several turns of the cable are wound on the ferrite ring of the magnetic core, near the place where the cable is connected to the antenna.
On my radio, this antenna is located on the inside of the window frame. It is attached to the frame with tape. The window frame with the antenna is located on the fourth floor of a five-story building, the window faces northeast, the house is reinforced concrete panel. I worked with this antenna with a power of 30 watts on the 14 MHz band, 10 watts on the 21 and 28 MHz bands. At the G36, in a short period of time, he had contacts with 50 countries: the CIS, Europe, Asia, Canada and the USA. QSOs were CW - 40%, SSB - 30% and some RTTY and SSTV contacts. Asia responded well in CW, about 1 contacts were made with JA From DX - R9MVI, 2M4, YB, XNUMXS.
It is desirable to use the KPI with a large gap between the plates, since it is located at the antinode point of the voltage (I used the KPI from a household tube radio with a capacity of 12/495 pF). To the full physical length of the frame web, the length of the conductors connecting the frame to the KPI is added. In my antenna, these conductors are half the length of the vertical side of the frame, and they are made of a two-wire "noodle" line. Antenna tuning is carried out by changing the capacitance of the KPI according to the minimum SWR, as well as by selecting the length of the conductors from the frame to the KPI.
Author: A. Sterlikov (RA9SUS)
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