[AMRadio] Dummy Load


Phil LaMarche plamarc1 at verizon.net
Mon May 19 14:02:49 EDT 2008


Can anyone advise where to purchase the Glo-Bar resistors.

Phil 


Philip LaMarche 
LaMarche Enterprises, Inc.
www.instantgourmetspices.com 
www.w9dvm.com 
800-395-7795 pin 02 
727-944-3226 
FAX 727-937-8834 
NASFT 30210 
W9DVM 
  


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of D. Chester
Sent: Monday, May 19, 2008 1:08 PM
To: amradio at mailman.qth.net
Subject: Re: [AMRadio] Dummy Load

>>I made a mistake about 35 years ago buying some "non-inductive 
>>resistors for a dummy load. The only place they were non-inductive was 
>>at 60 Hz. The carborundums are not in the category.
>>                                                 Joe W4AAB

I use a bank of a dozen 600-ohm 150w "Glo-bar" carborundum resistors to
achieve a 50-ohm dummy load rated 1800 watts continuous duty air-cooled.

I once picked up some so-called noninductive resistors that were wirewound
in two layers wired in parallel,  with the wire of one layer wound in
opposite direction of the other layer.  They would not work in a dummy load
without a series variable capacitor to tune out the reactance. I suspect
that type of resistor, which may be satisfactory for the AM broadcast, might
have substantial inductive reactance on the HF amateur bands.  With the
capacitor, mine worked OK.  I doubt if an ordinary wirewound resistor could
be made to work satisfactorily, since it would behave more like an rf choke
than a resistor at those frequencies.

Don k4kyv

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