February 1, 2010 YO5PBG Tips: The most complex part of a transceiver
Making a transmitter or the transmitting part in a trasceiver is the most difficult part seen by a newcomer .
It is not. It is what I call a standard job. The most complex side is the receiving part.
I like to use as possible passive double balanced diode mixers, the same for both RX and TX.
Always preced the preamplifier with a Band pass filter or at least a tuned circuit.
Don’t try to make too much high gain in the IF RX amplifier. I don’t see why you should use more than 1 or two transitors here!
Use dual-gate MOSFET as possible to implrove AGC dinamic. Bipolar transistor based cascodes (only a stage) are also good in IF stage, after the crystal filter. They offer very good gain and easy AGC handling.
No need for high gain front-end amplifiers for the RX stage (one stage – one transistor is enough, not only at HF, but also on VHF. If needed use a preamp. for VHF/UHF, directly connected to the antenna.
LM386 is my prefered AF PA. Who needs 3 to 10 watts for audio? You don’t listen Jean Michel Jarre on your tranceiver!
(to be continued)