Article: 3951 of rec.aviation.homebuilt
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From: AUNET@UWYO.EDU
Newsgroups: rec.aviation.homebuilt
Subject: Re: Rotax question
Date: 21 Jun 1994 13:08:51 -0500
Organization: University of Wyoming
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The Rotax 582 does in fact have a generator, it will produce about 17 
amps of power. This will give you just enough juice to run a low amp 
radio, gps, transponder and nav/pos lights and strobs. 

The biggest power draw will be from the lights. A typical Whelen 
strobe power supply will draw 7 amps and the strobes will draw 
another 8 amps for a total of 15 amps, leaving you 2 amps to work 
with to power everything else, kind of a drag. What I would suggest 
would be to purchase Whelen's low amp draw strobe power supply, which 
draws 4 amps. This unit looks exactly like Whelen's standard four 
strob power supply but only has 2 strobe power connections. This is 
kind of a special item so most retail dealers have to special order 
them from Whelen, but the price should be the same as a regular 
Whelen power supply ~$250.00. This then gives you five amps of 
power to work with, much better considering an average handheld radio 
will draw 1 amp of power while transmitting on high, a transponder 
another 1 amp and the GPS will draw about .75 amps leaving a little 
margin for power fluctuations. 

Speaking of power fluctuations in a Rotax generator, I would highly 
recomend using Rotax's higher quality rectifier/regulator ~$65.00. 
this unit I found to be much better than the cheap one. I would also 
use some kind of a power filtering device, this will make life 
a lot better for your electronics and also goes a long way in 
cleaning up ATN (Audio Tach Noice, that nasty buzzing in your 
headsets caused by the the electronic ignition that changes pitch 
according to the engine RPM). I have used a unit that I picked up 
from Radio Shack with good results. People also use them to filter
ATN in their car stereos. 

The power that comes off a Rotax will flutuate between 13 and 16 
volts depending on the RPM of the engine. With this flutuation I 
found it necessary to step the power down a couple of volts on the 
main power source for the electronic equipment. I did this by putting 
a couple of diodes in series in that wire stepping it down to an 
average of about 13.5 volts.

Well I hope I have helped, I gained this information through a lot of 
information gathering and testing. I have talked to just about 
everyone who deals with Rotax's except the people in Austria. 
This includes California Power and Kodiak Research the people who 
import them from Rotax in Austria. 

But of course these are my own findings and opinions.

Tom Aune
aune@uwyo.edu