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ANTENTOP- 01- 2009, # 011

Transceiver "POLEVIK"




By: Vladimir Polaykov, RA3AAE


Credit Line: CQ-QRP # 13 (magazine of the UR- QRP-C)


The schematic of the transceiver is just a project and required the practical test. Author will be really appreciated those who test the transceiver.


Schematic of the transceiver is shown on Figure 1. It is DC transceiver.


Transistors VT1 and VT2: They work like a mixer at RX mode and like a PA and doubler (key down) at TX mode.


It is necessary to use MOSFET with the "right" gate/drain characteristic. At such transistor drain current is absent when gate connected to source and voltage is across drain/source. To open the MOSFET you need connect the gate with DC in positive polarity (relative to source). Cutting voltage for such transistors may be 0.5- 2.0- V.


If you have no MOSFET with the "right" gate/drain characteristic you may use usual MOSFET with the "left" gate/drain characteristic. However at the case the MOSFET should be closed by some negative polarity across gate- source. Transistors VT1 and VT2 should be matched pair (have the same parameters).


Transistor VT3: It is Qurtz- RF Generator. It works at the same mode at RX and TX. Quartz has resonance frequency twice lower the working frequency. At RX/TX it should be some frequency shift that allows work at the transceiver mode.


Transistors VT4 and VT5: They work at audio amplifier. Transformer Tp1 is an ordinary output transformer from an old transistor radio.


Tuning and Adjustment: At first at transmitting mode (key down) tune the PA to maximum power. It does with help symmetrical L3 (find necessary numbers of turns) and tuning L4C7 to resonance (F/2). Maximum power into antenna (or dummy load) is depend on L1 and C1. PA tuned to the maximum power should provide maximum sensitivity at RX mode.


Attention: It should not be any current through VT1 and VT2 when the Quartz is removed.


73/72! De RA3AAE




Figure 1 Transceiver "POLEVIK"

Page 73





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