[AMRadio] Dummy Load


Donald Stanton tecair at bellsouth.net
Fri May 16 11:30:31 EDT 2008


----- Original Message ----- 
From: "Joe Crawford" <crawfish at surfmore.net>
To: <jc at pctechref.com>; "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Thursday, May 15, 2008 9:34 PM
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. 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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