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Tenner QRP 10m CW Transceiver


Small experimental CW 500mW transceiver using just 5 transistors

The Tenner uses the OXO circuit for the transmitter and an SBL1 (or similar) double balanced mixer based direct conversion receiver. TX-RX offset is around 600-800Hz when the key is pressed, so no special RIT circuit is included. The receiver is a decent one with a respectable performance for something this simple. If the SBL1 or similar is not available it could be substituted for a single balanced mixer using a toroid and 2 matched diodes.

I have now roughed out the schematic although I cannot guarantee all values are precise and will check these over when I have a little more time. On the circuit shown there is a switch to select two VXO ranges, but only one is fitted. 

Click on the schematic to enlarge it.

Note that the crystal uses a 28.06MHz fundamental crystal - NOT 3rd overtone. These are a little harder to find
but this gives more pulling range. Even greater pulling range can be achieved with a small inductor in series with the crystal but watch out as chirp may become excessive and the difference between TX and RX frequency less well defined. This is a basis for experiments - don't take the values as optimised. Have a go yourself and adjust the circuit to improve it further.



Specification 

TX Power               500mW
RX sensitivity       -110dBm
VXO range            25kHz (2 x 25kHz with second crystal)
TX/RX switching   Full break-in

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