Thoughts mostly as applied to making ubitx or bitx modular. From start good idea.
Breaking it into modules allows one to solve issues as they arise like power amp
isn't good enough build and replace a new one. IT takes all the ugly fixes out as
now a module deemed less than desired can have a new or modified one substituted.
Now lots of questions:
Many of the uBitx problems are related to:
Board layout (many cases of good circuit compromised)
Filtering circuits (and their layout)
Gain distribution, some places not enough other way too much.
Power amp performance (power fall off and instability).
These are for TX path only:
How much gain is planed for the path starting at the balanced modulator
(not the audio before that is also low gain) though all the filters and possible
mixer to the last mixer?
How many devices are needed to supply that?
How much audio gain, gain control, or compression?
once you have a signal(s) at the last mixer what is the filtering scheme to
insure a reasonable spectral purity ant the input to the power amp?
How much gain and its distribution in the power amplifier?
Just an opening set of questions.
Building a radio is like building a house or bridge, you need an idea of what
size and how its going to look. The foundation must be sound and support
the planed design. For a Transceiver that is the basic RF core. Everything
else builds from there.
Also for the moment unless the MCU is doing DSP its not part of this save
for its integration must be clean referring to the paths from 5351(s) to the
various points that signals are needed. The MCU is the user interface only
and as stated unless its doing DSP it cannot enhance the signal.
On a different path.
Items I see as useful as in should have:
*SWR/power out measurement built in its trivial and everyone needs that.
*Ways and tools built in to help diagnose. Others have done this and please
read the Elecraft K1 and K2 manual if this is not clear. Its handy for those
without lots of gear and a kindness for those of us that will use it.
* Consider BITE, Built In Test and Error report. It can as simple as
measuring the 12V in to assure you have enough DC power during
transmit! Another could be excess SWR, Excessive PA current (from
high SWR or Fault). Simple and easy measurements.