40 meters CW Transceiver

Posted on Aug 23, 2012

This project describes a little QRP transceiver full legal power” (5 W at 12 V) for the 40 meters band. The RIG may be built in a gradual manner, in fact it is divided in two main modules, or you may also complete only the RX module. The RX section is designed so as to allow receiving both SSB and CW signals on the whole 7 MHz band. The tuning may be done using only an HF receiver, but if you have at your disposal a frequency meter and a signal generator, you could do a better job. If you are interested in further informations, or to get the PCB masters, please contact me at my E-mail box.

40 meters CW Transceiver
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40 meters CW Transceiver - image 1
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The transceiver is composed by two single sided printed boards 100x66 mm. These should be fixed on a metallic ground base, and possibly enclosed in a little metal cabinet. On the front panel you may place the tuning potenziometer (a 10 turns model or a single turn device with a reductor gear) and the gain control. The frequency reading may be obtained with a 200 µA panel connected to the tuning pot. The Key and earphone jacks, like the power and antenna connectors may be housed on the back panel. You may give a nice look to the panel by drawing a 1:1 mask with a common graphic tool (I use the MS POWERPOINT), and then printing it on a self-adhesive transparent. The whole process may seem to be a little laborious but the result is very attratctive. The Receiver circuit It uses a classic superetherodyne design, for simplicity purpose I didn't implement an IF stage with a related AGC circuit, this is a compromise choice and implies some manual sensitivity adjusting in presence of strong QSB. The overall sensitivity and selectivity are very good and so also the capability to handle strong overloading signals, proving the effectiveness of the preselector stage and XTAL filter. The Transmitter circuit I employed a frequency conversion approach, in this manner it is possible to receive and transmit on the same frequency using a single VFO. An automatic RX/TX switching circuit implements the full breakin and monitor...

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