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

[JAMES T BRANNIGAN]

> 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.

At one time that was true, but not in the last 20 years.

> 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.

If I survive an airburst, the least of my problems will be the state of my
radio.

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.

That has less to do with the radios than the Army's penchant for fighting
the last war.  I'm surprised the Infantry wasn't issued parkas and skis.

> 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.

Finally, a reasoned argument.

> 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.

When you hook an antenna up to an HF radio, atmospherics will mask all of
that.  The noise floor is the broken thermostat in the neighbors house.

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

Also, a well reasoned argument.