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[AMPS] Cantenna Dummy Loads

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Subject: [AMPS] Cantenna Dummy Loads
From: (
Date: Sat, 6 Feb 1999 15:07:03 -0500

On Thu, 04 Feb 1999 18:21:47 "Phil T. (VE3OZZ)" <>
>If they're wire wound, they ain't non-inductive at RF (at AF maybe).
>Anyhow, the 1990 ARRL HB has a nice dummy load project. It uses a true 
>non inductive resistor in 2 gallons of oil that will safely run 1500 
>for 10 minutes.  The actual power rating of the resistor was 
>around 100 to 200 watts.


That article did a nice job explaining the dynamics involved with heat
transfer and frequency response. Taking it a step further you can extend
( add another 1 gallon can) the Heath Cantenna into a 5 gallon can and
get similar results. The Heath uses a 50W resistor wheras the Handbook
article uses a 100W version in the HF load. 
The Handbook UHF Super Dummy uses  a 50W resistor ( even references the
Heath Part #) and will handle 1000W for 5+ minutes. 

Note both articles go into detail on coolant dielectric constant. Dont
expect to just drop a resistor into some used motor oil and expect it to
work. That would be something my wife's NFLD, Neewfie relatives would try
 before it burnt the saloon down!

73  Carl  KM1H

>At 12:34 PM 2/4/99 -0500, you wrote:
>>That being said, several years ago I built a 50R load containing 
>>series/paralled 100R non-inductive wire wound resistors in a 14" x 
>17" x
>>4" enclosure which was force air cooled. Since the load as built was
>>slightly reactive, a series variable capacitor within the enclosure 
>>used to provide a near perfect 50R match. This load easily handles up 
>>two killowatts for any amount of testing time that might be 
>>Total cost as I remember it was under Can.$40.   
>>You may communicate with me by using any of the following 
>>FAX:          905-294-8756
>>Telephone:    905-294-8527
>>Canada Post:  C.S.Broad
>>              32 Wootten Way N.
>>              Markham ON
>>              L3P 3L9
>>              CANADA
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