Concept - The Next Steps

So where do we go from here? I have decided to split the Concept program in two parts:

1. A Concept program for beginners

2. A development of the current program towards a complete Transceiver.

Beginners

For beginners a more simple pair of shields will allow them to build a receiver and, most importantly, learn basic coding of Arduino Sketches. The existing VFO Shield can be simplified by not including the Real Time Cock module, A low cost 16 x 2 line LCD can be used, and a new Direct Conversion receiver shield can be designed and added.

A new, simplified sketch will provide just the VFO tuning for the 40m Band.

This is the new DCRX:


It uses one of the most common circuits for a simple DC RX, using a balanced mixer followed by an audio amplifier. The circuit has been copied and emulated many times. What I have tried to do here is to simplify it to the most, both for the mixer stage (SA612 or SA602 device) with a band pass input filter, and direct push-pull output to the audio amplifier. And a simple audio stage using the LM386. The LM386 includes input resistors so no external one are needed, and its gain can be adjusted by feed back - giving a gain of x1 -200 - so here an external 5K pot is used as a volume control. This is the board out:



The beginners VFO software sketch has not yet been written, but will be published when the DC RX prototype is built. It will be "modular" so that beginners can follow how it is made up of the various functions.

Extending Concept

To extend the Concept full program further shields are being designed:

1. A Low Pass Filter with built-in SWR metering - with display on the LCD screen.

2. A Transmitter shield, using SDR techniques to output all modes LSB/USB, CW etc under software control. This transmitter shield will have a very low output, in theoriser of 5mW, so will required a PA to build a full QRP rig.

3. A PA with input at 5mW and output of 2-5W (it is yet to determine how to absorb the heat generated in the output stage.

All of these three developments have been drafted and are included below, the LPF_SWR shield is in prototyping right now.







More about these designs to come.