[Milsurplus] 115 VAC 400 hz power

[Mike Morrow]

>115 VAC at 400 hz was also used as input for the power transformers in
>some WW2 aircraft nav gear such as SCR 269, ARN 7, APN 4, APN 9 etc.

As far as I can determine, all that aircraft 400 Hz power came from
inverters.  The -1 flight manual (24APR51) for the B-29, 29A, and 29B
(likely the WWII aircraft with the most need of 400 Hz power) indicates
that all those loads requiring such power (including the "Raven"
countermeasures gear) got it from multiple relatively small 28 vdc input
single-phase rotary inverters.

Engine-driven 400 Hz generation would be complex, given the requirement
for a specific constant speed input to the generating system.  (Today's
modern systems haven't that problem.  Honda's EU2000, for example, uses a
microprocessor-controlled variable-speed engine to drive an alternator,
whose output is rectified and fed to a microprocessor-controlled static
inverter to produce some of the cleanest pure sinusoidal 60 Hz at constant
voltage that a portable gasoline-powered 2 KW generator has ever produced.)

>I've been tempted to amplify the output and fire it up on the 160M band to
>give the old timers a jolt, but sanity prevailed. The sound of LORAN A
>signals is something the old timers on Top Band will never forget. 

One need not be an old-timer to remember 160m LORAN A signals.  The USA
didn't close its LORAN A service until 31DEC80, a mere blink-of-an-eye ago.

Mike / KK5F

(I bought my R-65/APN-9 LORAN A at John Meshna's store in Lynn, MA, in 1976.
An AN/APN-9 was installed on the Royal Netherlands Navy Destroyer Hr.Ms.
Amsterdam, on which I was assigned in 1973, but in the North Sea we used
the UK Decca Navigator instead as the preferred hyperbolic radio-navigation
system.)