TRAN-C converter. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / radio reception

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The proposed converter is the first in a series of TRAN converters. On its basis, the VHF converter described in [1] was developed, and much of what was said there is also true for the proposed converter. I consider it necessary to provide only additional information.

The sensitivity of the converter is low, which implies the use of this converter only as an auxiliary one, used to check and adjust the equipment and for communication over short distances. The converter is quite broadband and allows you to transfer the entire two-meter range to the broadcasting VHF FM.

The converter (Fig. 1) is designed to work in the TRAN (Tyumen Radio Amateur Net) network at a frequency of 145,5 MHz in conjunction with any broadcasting FM radio receiver. It consists of UHF (VT1), mixer (VT2) and quartz local oscillator (VT3, VT4). All coils are frameless, wound with a wire with a diameter of 0,6 mm on a mandrel with a diameter of 6 mm.

LI - 5 turns, branch from 1,5 from the cold end; L3 - 5 turns; L4 - 11 turns, tap from 1,5; L5 - 15 turns (for he - 13 MHz); L6 - 9 turns, tap from 4,5. Ferrite rings are put on the outputs of the bases VT3 and VT4 to the output of the drain VT1. L2 - throttle DM (0.1-100 μH).

Installation completedon "piglets" on a 110x55 mm board made of double-sided foil fiberglass. "Piglets" marked with a cross are drilled through, countersunk from the reverse side, power is supplied through these holes.

The converter has small dimensions, is simple in design and can be manufactured in the shortest possible time. There are two screens on the board: one shields the local oscillator from the URF and the mixer, the other shields the mixer from the URF.

The body of the converter can be made by soldering the board along the perimeter with strips of fiberglass, as was done in [1]. The use of tinned "white" tin in this case leads to a microphone effect due to the large dissipation of the local oscillator energy associated with the low quality factor of the coils, the absence of screens on the coils and the small dimensions of the device.

The simplicity of the design and the selected local oscillator circuit, in which even low-active quartz resonators are excited, as well as the absence of band-pass filters, contribute to the appearance of side reception channels, for example, via the image channel. This must be taken into account and the design of the converter should be treated with understanding. The quartz resonator in the local oscillator is excited at the 3rd harmonic (39 MHz), followed by doubling - 78 MHz, then the signal is fed to the mixer. Frequency. local oscillator-may vary depending on the presence of quartz resonators and an IF free from broadcasting stations. The converter, in principle, can be added to VHF FM radio receivers operating at low frequencies - 30-60 MHz (for example, the Len, Granit series). Along the screens, it is desirable to "flash" the board with pieces of tinned wire and solder it on both sides, as was done in [1]. When tuning the local oscillator, it is desirable to use a resonant wavemeter, the amplitude of the harmonics in this generator circuit is very large, and you can make a mistake.

Literature:

1. V. Besedin. VHF converter at 144 MHz. Radio No. 9/1991 pp. 22-25

Author: V.Besedin (UA9LAQ), Tyumen; Publication: N. Bolshakov, rf.atnn.ru

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