Variant of alteration of the transmitting attachment (UA1FA). Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Civil radio communications
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The figure shows a diagram of frequency conversion units that can be used in a transmitter designed by J. Lapovka (UA1FA). They do not have any features in their construction, but together they provide the same signal level (about 2 V) at the input of the pre-amplifier in the ranges from 1,8 to 28 MHz. A local oscillator is assembled on transistor VT1, which generates oscillations of a fixed frequency of 5 MHz, on VT4 - an IF amplifier.
(click to enlarge)
The first mixer is a diode ring (VD1-VD4), the second is balanced on transistors VT6, VT7. Cascades on transistors VT1, VT2, VT5, VT8 - matching. The establishment of this conversion path is reduced to balancing the transistor mixer with resistor R21 until the GPA signal disappears at the output and adjusting the coils L1, 12 of the bandpass filter at a frequency of 5,5 MHz to the maximum signal at the same output. Coils L1, L2 are wound with PEL 0,31 wire on a frame with a diameter of 9 mm and contain 20 turns each. The coils are spaced 12mm apart. Transformers T1-T4 are made on a ring (size K7X4X2) magnetic core made of 600NN ferrite. The windings of each of them are wound (16 turns) simultaneously with PELSHO 0.2 wires pre-twisted together (three twists per 10 mm).
Author: V. Fishchenko (RA0AAF), Krasnoyarsk; Publication: N. Bolshakov, rf.atnn.ru
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