Xref: utzoo sci.electronics:5909 rec.audio:12363
Path: utzoo!dptcdc!jarvis.csri.toronto.edu!mailrus!ames!ncar!noao!arizona!naucse!rrw
From: rrw@naucse.UUCP (Robert Wier)
Newsgroups: sci.electronics,rec.audio
Subject: Re: Who has dummy speaker loads?
Keywords: dummy, speaker, load, watt
Message-ID: <1352@naucse.UUCP>
Date: 18 Apr 89 22:25:45 GMT
References: <3474@nunki.usc.edu> <382@sagpd1.UUCP>
Distribution: na
Organization: Northern Arizona University, Flagstaff, AZ
Lines: 27



 Regarding audio dummy loads...

 I once used (many years ago) a light bulb to tune up my amateur
 radio transmitter.  Kind of neat to see the light flash in synch
 with your voice on SSB.  However, it's not recommended because 
 1) the load is complex (lots of inductance), 2) the resistance of
 the filament changes as it heats up and cools down and 3) it 
 radiates (leaks) rf.  I once made a 500+ mile contact on a 
 50 watt light bulb (ahem...)

 Heathkit sells a "Cantenna" which is basically a one gallon paint can
 with a 50ohm resistor suspended inside.  The idea is that you fill
 it with mineral or transformer oil which will circulate and dissapate
 any heat.  Its rated up to 1,000 watts up to a frequency of 450 Mhz.

 I would suppose you'd want something in the range of 4-12 ohms for
 audio work.  I note that in the Newark catalog they have Dale high
 wattage resistors.  You could parallel, say, 5 20W 100 ohm values
 and come out with something usable.  If you stick 'em into a 
 cantenna, the rating would be considerable higher...


   - Bob Wier                                College of Engineering
  Flagstaff, Arizona                      Northern Arizona University
  ...arizona!naucse!rrw |  BITNET: WIER@NAUVAX | *usual disclaimers*