[Milsurplus] PU-18/A ???

Richard Brunner rbrunner at gis.net
Sun Oct 8 19:48:27 EDT 2006



David Stinson wrote:
>>The PU-18/a is a 28 VDC input 'screaming mimi' with an 800 Hz 115 VAC
output. Wonder if you could turn the inverter with an external AC motor and
> avoid the screaming?

Not a chance.  It's mostly magnetostriction.  Dennis, W7QHO, on the west 
coast has the motor-generator, and it screams too.  he disabled the 
generator excitation, thinking it might be a bad bearing, and there was 
merely windage, bearing and commutator noise, meaning not much.  60 
cycle motors are probably noisy too, but we don't hear so good at 120 
cycles, and it may not couple to the air as well at 120 cycles as at 
1600 cycles.

I saw that inverter at Hosstraders, and it looks exactly like my 800-1, 
but with an additional plug on the side.  It must be an early one, as 
later ones are rated 10.5 amps, vs 7 amps.

FWIW, I measured 91 dB at three feet, about the same as a subway train 
running through the shack.

Richard Brunner, AA1P


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