[R-390] Reasons NOT to Solid State a 390

[James Miller]

1- Dynamic range of a tube receiver typically better than solid state. 
Tubes run at high voltages, solid state devices run at low
voltages, hence in general tube front ends have much better dynamic
range.  Better strong signal handling capability.

2- Resistence to EMP and Static Discharge.  These days, don't laugh, it
could happen.  Watch the news.  If you survive the burst, you're 390
will still work.  Your $4000 Icom radio probably won't.  Also, in
general a tube rig will be less suscepitle to static discharge.  During
Desert Storm, the high tech solid state radios would be damaged by
static discharge on antennas caused by sand storms.  They had to rush in
some KWM-2 tube rigs as backup.  So much for solid state.

3- Design incompatibility - The unique capabilities of the 390 depends
heavily on very high impedance tube circuits.  The AGC is an example. 
The multiple stages of preselector and mixer tuning were carefully
designed, mechanically and electrically, for high impedance tube
circuits. Solid state is typically lower impedance, even FETs.  If you
replace the front ends with solid state, your preselector and mixer
tuned circuits may not have the same Q and will probably not be as sharp
in bandwidth.  Hence, even more susceptibility to out of band strong
signals and intermod.

4- Noise floor - Assuming you also upgrade the LOs and PTOs to solid
state PLL circuits, your noise floor will get worse due to phase noise
from the PLL's.

5- Why bother?  If I want a solid state radio, I'll go buy one designed
for solid state devices.

Any others?