[Amps] Non-inductive resistors

[Bill Fuqua]

There would be too little magnetic coupling from two series resistors wound 
opposite directions for the field to cancel.
Some N.I. wire wound resistors have two opposite direction wound coils such 
that they cross and connect twice each turn. This simulates a uniform 
cylinder.  I have had some of these in the past but even these sometimes do 
not work well above 5 or so MHz.

73
Bill wa4lav


At 03:43 PM 9/28/2004 -0400, craxd wrote:
>Mike,
>For smaller loads, I'd use a Globar resistor also. For the 20 Kw load, and 
>to homebrew one with limited resources, they might look into this. I was 
>thinking about those large grid resistors. If one had two of them, 25 ohms 
>each, but wound in opposite directions, it might work somewhat by 
>seriesing them. This would be the same as that dual wound resistor in two 
>sections with the different hand coils. The bifilar has a lot of 
>capacitance due to the potential difference between the incoming and 
>outgoing resistance wire. But, if this was broken up like the mentioned in 
>sections, it may work also. One would have to use some sort of alloy 
>tubing with the highest resistance you could get. For 20 Kw, were probably 
>talking something like 3/4" diameter tubing with maybe a 1/8" thick wall 
>or larger. Inco Alloys (Now named Huntington Alloys), has both the alloy 
>mill (Huntington, WV.), and the tubing plant just down the road in 
>Burnaugh, Kentucky. They make about every nickel alloy, (Inconel, Monel, 
>etc.), and others you could mention. I had a friend who retired there and 
>he may know about this, I'm not sure. Even using that figure eight pattern 
>might be better. It has a figure eight wound every other turn so to 
>continuously reverse the current flow from one turn to the next. With 
>stiff enough tubing, this might be done without using a coil form.
>
>I'd like to experiment with this some myself just to see what will work 
>and what will not. For loads of 5 Kw and down, I'd stick with the Globar 
>resistors.
>
>Will Matney
>_______________________________________________
>Amps mailing list
>Amps at contesting.com
>http://lists.contesting.com/mailman/listinfo/amps