Return of the Simpleceiver Plus!
8/20/2017 ~ I have already received some feedback from several readers about their desire to participate in this project. So here is a little more information about how the project will progress.
There are many ways to initiate a radio project with some advocating building the toughest nut to crack as a first item such as the Analog VFO or a Digital VFO and then follow on with the easy stuff. While my preference is to always start at the back end and work your way forward so that what is built and tested then becomes part of the test system for the next stage to be added. That is how this Simpleceiver Plus project will progress and the first element will be the audio amplifier stage.
My plan is to try to use / reuse a common circuit in as many places as possible since that affords an opportunity to minimize the numbers of different parts used and a common building block enables/facilitates trouble shooting. That common building block is two J310s configured (mostly) as a Dual Gate MOSFET (DGM). I now have this common J310 DGM circuit element configured as a Microphone Amplifier, RF Amplifier, IF Amplifier, Oscillator, Mixer and Product Detector -- we are just getting started here. Along with this is the extensive use of LT Spice Simulation software (a free download from Linear Technology). Thus you have a solid technical basis for the design that has been simulated with known results and thus enables experimentation to evaluate circuit changes and improvements.
Because the DGM has four connections much like a Tetrode vacuum tube, Gate 2 affords us the opportunity to use this port as a secondary signal input port for applications such as in a Mixer or Product Detector. If however a variable voltage is applied to Gate #2 it then becomes a variable gain amplifier stage which is desirable for application involving the addition of Manual Gain Control or AGC. Hopefully you are now seeing the rationale behind my choice of design approach. Stay Tuned!
There may be a good chance of a group project being undertaken called the Simpleceiver Plus, much like the LBS project. Only this time it will be done incrementally with hopefully the blog readers following right along as we build first a Direct Conversion Receiver and then either a DSB Transceiver or an uptown SSB Transceiver.
In line with keeping it simple get a stock of J310 FET's as these will form the basic building blocks for the project. Most of the circuits will use homebrewed Dual Gate MOSFET's made from two J310's. In many cases LT Spice Simulations will be provided so that the builder can "tinker" with the circuit elements.
Below are two videos where you can see & hear the Simpleceiver in action. Yes, initially it has the dreaded Analog VFO and a homebrew Crystal Filter built NOT Using the Dishal Method. Listen closely to how the filter sounds. The IF is at 12 MHz so a 5 MHz LO gives you the 40 Meter Band.
Let me know if you would be interested in building along with me on this project.