FOUR BAND CW TRANSCEIVER WITH DIRECT CONVERSION

  
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The performance of the 80 meter CW transceiver using the phase method for side band suppression is very good. Construction was easy with all good obtainable standard electronic components and without the expensive or complex crystal filter. Almost nothing is heard on the unwanted side band. Therefore I had the plan to make a four band version to s
FOUR BAND CW TRANSCEIVER WITH DIRECT CONVERSION - schematic

ee how the performance of the phase method for suppression of a side band is for other amateur bands. But it had a lot of disadvantages. No 30 meter band, some frequency drift, no accurate frequency read out, a double side band direct conversion receiver, spurious emissions did not comply with the current limits. There were a lot of problems with 50 Hz hum due to the audio transformers and 88 mH inductances in the filters. Therefore, it was time for a restoration. I decided to dismount all the old printed circuit boards and keep them as a memory. Only the enclosure is used again, the damaged paint due to the intensive use in the shack and mobile while sailing is left in original state. It should become a four band version of the 80 meter band CW transceiver with the phase method used in the receiver. Adding the 30 meter band and also a simple frequency counter were the most important wishes. The antenna signal is routed through a RF attenuator potentiometer to the four preselector circuits. It was easier to make four different RF amplifier than one with input / output switching circuits. The RF signal is split into two signals that are shifted 90 degrees out of phase (one plus 45 and one minus 45 degrees). Both are mixed to audio frequencies. The two audio signals are again shifted 90 degrees out of phase (again one plus 45 and one minus 45 degrees). When we add the two signals, the signals of one side band are in phase,...



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