A simple 50 MHz band transverter. Scheme, description

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A simple 50 MHz band transverter. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Civil radio communications

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This transverter design for the 6 m range is based on the development of the Dutch PA3FYM radio amateur described in [1]. It is distinguished by extreme simplicity and the absence of scarce details. At the same time, the transverter has sufficiently high characteristics, and when working with any KB transceiver with 14, 21, 28, 29 MHz bands, it is suitable for full-fledged operation on the 50 MHz band. In the presence of all the details, manufacturing and setting up takes no more than one day.

Although the 6 m range in different countries occupies the frequency band from 50 to 52 MHz, and in some places up to 54 MHz, 99% of all communications are carried out in the 50,080 ... 50,200 MHz section. Therefore, the range of 14 ... 14,35 MHz was chosen as an intermediate frequency. This allows the use of non-deficient 12 MHz quartz in the crystal oscillator. The ranges of 21, 28, 29 MHz and, accordingly, quartz at 29, 22,21 (7) MHz can also be used.

The schematic diagram of the transverter is shown in the figure. It consists of a crystal oscillator (KG), a reversible mixer (SM) and a bandpass filter (PF), a single-stage high-frequency amplifier (UHF) and a two-stage power amplifier (PA) with a low-pass filter at the output.

Schematic diagram of the transverter (click to enlarge)

Switching TX / RX on HF and LF is carried out using small-sized relays. Transformers Tr1, Tr2 are wound on 50 VCh rings. Tr1 contains 3x8, and Tr2 - 2x5 turns. L1 is wound on a frame with a diameter of 7 mm and has 11 turns. L2, L3, L7 - frameless, wound with 1 mm wire on a mandrel with a diameter of 7 mm, 10 turns. Withdrawal - from 1 ... 3 turns. L3 - choke, 3 turns on a ferrite rod with a diameter of 3 mm. L5, L6 - frameless, wound with 1 mm wire on a mandrel with a diameter of 5 mm and contain 5 turns each.

The transverter is mounted on a double-sided fiberglass board the size of a postcard. The installation was done on the "spots".

Setting up the transverter

The UHF and PF circuits are tuned to a frequency of 50,1 MHz. The circuit in the VT1 collector is tuned to a frequency of 36 MHz. Setting the PA is reduced to setting the initial currents VT3 and VT4 (respectively 20 and 50 mA).

The output power of the described transverter is 0,5...1 W. This is quite sufficient for carrying out many bonds under Es-transmission conditions. It is possible to increase the output power to 8 ... 10 W using a power amplifier from the Granit radio station, for which it is necessary to adjust the circuits and transfer the transistor modes from class C to class AB.

Our attempts to match this transverter with the amplifier described in [2] were not successful.

What and when can be heard on the 50 MHz band

This band is often referred to as the magic band because it combines features of both the HF and VHF bands. In May-June, the range lives due to Es-passage. To work in the sporadic at 6 m, the most primitive antenna (a dipole in the attic) and a power of 1 W are enough.

With an increase in solar activity, F2-passage appears, and intercontinental communications can also be carried out at this time.

Radio amateur beacons (they are in the frequency band 50,000 ... 50,080 MHz) and television transmitters of the first channel (at frequencies of 49,750 MHz in the CIS countries and Eastern Europe and 48,250 MHz in Western Europe and Southeast Asia) can serve as indicators of passage on the range . To listen to these frequencies, the described transverter with a separate receiver is suitable. Long-range television reception on I...III channels and FM broadcasting in the VHF band 65...74 MHz indicate good conditions on the 6 m band. The 50 MHz band has been allowed in almost all European countries with or without restrictions over the past 10 years . As of the end of April 1997, it remained completely banned only in Ukraine, Monaco and Hungary.

Talk about interference with television has been refuted by amateur radio practice. Today, the permitted power in Denmark is 1 kW, in the UK - 400 watts.

The most common 6m band antennas are 3...5-element Yagi. But for the first case, a simple dipole 2,84 m long is also suitable.

Permission to describe the adapted PA3FYM design has been obtained from the author.

Literature

R. den Besten (RA3FYM). 50 MHz WAT (Werkt Altijd Transvertor), Electron, December, 1995.
Grishchenko S. (UA3QHP). A simple 50 MHz band power amplifier - Radio amateur. KB and VHF, 1995, September, pp. 27 - 28.
Current VHF/UHF Beacons - Radio amateur. KB and VHF, 1996, No. 3, p.2 - 3.

Author: A. Gavva (UR4LL), Ukraine, Kharkiv region, Zolochen settlement; Publication: N. Bolshakov, rf.atnn.ru

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