[AMRadio] Dummy Load


Joe Crawford crawfish at surfmore.net
Thu May 15 21:34:24 EDT 2008


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. IIRC, the PEP output would be 4 times 
the carrier with 100% modulation, hence, a kW out of carrier(which is too 
much for amateur purposes) would be 4 kW out. This is why the 375 watt level 
gives 1500 watts PEP(thanks to the 1990 power reduction[sarcasm inserted].
                                                 Joe W4AAB
----- Original Message ----- 
From: "John coleman" <wa5bxo at gmail.com>
To: "'Discussion of AM Radio in the Amateur Service'" 
<amradio at mailman.qth.net>
Sent: Thursday, May 15, 2008 4:36 PM
Subject: RE: [AMRadio] Dummy Load


Hi Rick:
Some time ago I located 12 - 600 ohm 100 watt or more non inductive
resistors.  I purchased them from http://www.goldmine-elec.com/.  They are a
surplus dealer.  My plan was to build a dummy load by paralleling all of
them in an air vented box but I never got to it.  Some day I will.  In the
mean time that is what I recommend for you to look for.  These are long
(maybe 10 - 12") snap-in resistors about 1" diameter made of "carborundum"
or something like that, with silvered ends for snapping into large 1"
sockets on standoffs.

Good Luck
John


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Rick Brashear
Sent: Thursday, May 15, 2008 1:35 PM
To: 'Discussion of AM Radio in the Amateur Service'
Subject: [AMRadio] Dummy Load

I know this has been beaten to death many times, but for the sake of an old
man with a bad memory could we discuss the most economical (very important)
way to provide a dummy load for testing a broadcast transmitter.  I have a
few Cantennas, but they get hot real quick at 1000 watts and I'd like
something I could be a little more confident in.  If I were to use the
proper number of series/parallel non-inductive resistors at say 100 watts
each, what kind of support system would be best to insure at least a one
minute key down time?  Would immersing them in oil or attaching them to heat
dissipating metal with a blower be the better choice?



Thanks for any and all advice you may offer..



Rick/K5IAR

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