Frequently I am asked where is the complete schematic for this project. Often this comes more as an excuse than a real need. When the commercial guys start a project, it starts with a block diagram and a listing of requirements!
Much is to be said for my approach as the project can be chunked down into modules and divided up amongst the specialists for a detailed design in the commercial world. This has the advantage that a Module can be updated without throwing away the rest of the block diagram!
True the all important module interfacing always represents the challenge and that is where part two, the requirements listing, comes into play. In effect the Module designer has the freedom of choice so long as the Module takes a specified input, does its thing and provides a specified output!
The Module approach provides a built-in experimenters platform -- want to test a new device or new approach -- have at it, only do it one Module at a time then you can make the A/B comparison as all other factors are controlled.
But today I want to go one level deeper and that is the module components themselves. These I call my standard components. They include the 2N3904, 2N3906, 2N2222A, 2N2219A, 2SC5706, IRF510, NE602, ADE-1, MC1496, BF998, J310 and the newest member the BFR106. With these 12 devices I have built numerous, (>50) SSB and CW Transceivers.
Let us take an example of my standard IF Module where I have used an Amp #1, a Filter and Amp #2. The amplifiers (Amp #1 and Amp #2) have used the 2N2222A (P3ST), the J310s wired as a DGM, the BF998 (DGM), the 2N3904/293906 Plessey circuit (Shirt Pocket SSB) and the BFR106 (P3STV.2), The IF Module has been Bias Switched, Diode Steered and Relay Steered. Thus we are not stuck using the Bitx Module design nor the TIA Modules. In effect, we have the freedom to chose various devices and methods for bi-directional operation. This also lets us correctly impedance match the In/Out to 50 Ohms in both Receive and Transmit.
One of my innovative designs used a NE602 for Amp#1 and Amp#2. The innovation: Amp#1 was the Receive Mixer on Receive and the Balanced Modulator on Transmit while Amp#2 was the Product Detector on Receive and the Transmit Mixer on Transmit. That was an efficient design -- try that with your TIA!
For the Driver Stage I have used the 2N2222A, the 2N2219A or the 2SC5706. BTW the 2N2222A and the 2N2219A are the same device with the difference being the device dissipation.
For Balanced Modulators I have used the MC1496, NE602 and the ADE-1. The same line up for Product Detectors and Mixer stages.
Regrettably the MC1350, 40673 and BF991 are nearly impossible to find or priced through the roof.
Now I can see a few blog readers choking over the SMD stuff. Well choke no more! The BF998, ADE-1 and the BFR106 are sold by Todd, K7TFC at https://www.mostlydiyrf.com mounted on a circuit board. W1REX and Marlin P Jones & Associates (MPJA) sell carrier boards so you can mount the MC1496 and the SA612 SMD versions (SA612 = NE602) on the carrier boards and then they can be fitted to your project.
So when you are filling the bin list think about your dozen or so devices that you would stock and then you are ready to solder.
73's
Pete N6QW