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.
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).
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.
VT4 and VT5: They work at audio amplifier. Transformer Tp1 is an
ordinary output transformer from an old transistor radio.
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.
It should not be any current through VT1 and VT2 when the Quartz
73/72! De RA3AAE