mikem wrote:
I have had exactly the opposite experience. It is easier to suppress an
electronic regulator than it was to suppress the mechanical
regulator...

ADF (and Loran, remember those?) operate at low-rf frequencies between
100Khz and 500Khz. The "frying bacon" noise that effects these is
usually generated by arcing as the brushes jump across the segmented
commutator in a generator, or arcing as the brushes rub on the
slip-rings in an alternator. This happens regardless if the regulator
is mechanical, electronic or is not there at all...

I don't think we actually disagree. First off, the
alternator/generator noise is independent of the regulator... If it's
arcing and sparking, then that needs to be addressed regardless.

Second, the mechanical regulator does put out higher amplitude "spikes"
- but they tend to have less power in the higher frequencies than the
digital regulator, and they are MUCH MUCH less frequent. [Basically,
the mechanical regulator only "adjusts" in a few discrete quantum -
whereas the digital unit is constantly switching.] The result is that
the pops and clicks from the mechanical regulator don't tend to
interfere with the ADF and Loran, whereas the higher constant noise
ground floor from the digital unit does.

None of this matters if the regulator has proper grounding and
shielding, and minimal care is made to not run sensitive antenna wiring
and radio power/audio lines bundled with regulator wiring... but in
older planes with mechanical regulators they *could* (and hence *did*)
get away with it.

jmk