Here is another one for the idea box.
While I am doing stuff for much higher frequencies I am still thinking of this in connection with my "one QSO per band with home made gear" challenge. I was thinking of using a kit (or two) for a simple HF CW transceiver using a direct conversion receiver.
Some examples of those kits are the Pixie, the Rockmite, the Frog Sound and the 49'er. I have a box with some of those kits, and some of them should be quite easy to convert to HF bands up to 18MHz without too much loss of performance.
For higher frequencies I suspect that the receiver sensitivity will be insufficient for efficient work on those bands (21/24/28MHz). Here it is probably a good idea to use two kits, one for TX and one for RX, adding a preamplifier for improved RX sensitivity, and possibly a PA for higher TX power.
Each transceiver would be modified to use a SI5351 synthesizer board. This board should be controller (programmed) by, e.g. an Arduino, so I will have to learn another skill: Micro-controller programming. There are libraries and some programs in existence, but the programming skill will come in handy if I want to extend functions.
A simple 28MHz model could possibly be used as base transceiver for transverters to higher bands. This would not need RX modifications and could possibly be using just a simple TRX kit. I am well aware of the lack of CW activity, especially on the VHF/UHF/SHF bands, but a single QSO, or a few, should be possible.
I do have two other kits for CW transceivers, the QRP Labs' QCX+, with components for 20m and 60m. Still need to be built, but that is a matter of finding time to add those.
Do I have too many kits and projects? Yes, but I will not have any time to be bored, that is certain ...
Another one of the ideas stacking up ;)