Interesting... I looked up Aryton-Perry winding as a result. The Wikipedia
entry pointed out ...
"One disadvantage is that because the two lengths of resistive wire are
connected in parallel, four times the length of wire (twice the length for
each coil) is needed to make a given resistance than if a single coil was used."
That led to the realization that the two windings have to carry the same current
to have the magnetic fields cancel...which means they have to have the same
resistance.
Conclusions...
- start with 100 Ohm wire wound resistor
- count the turns
- wind 100 Ohms worth of copper over the same length
- for same turn count, need smaller diameter wire
jeff, wa1hco
On 02/03/2012 03:23 AM, Angel Vilaseca wrote:
> Hi all
>
> I have a nice large 50 ohms wirewound resistor, which I would like to
> use as a dummy load. Problem is, it is inductive of course.
>
> To cancel the inductive reactance I was thinking of winding some
> enameled wire all along over the resistor, with as many turns as the
> resistive wire, solder the enameled wire to the resistor terminal at one
> end and feed the RF at the other two separate terminals (wire and
> resistor) at the other end.
>
> The idea is that the inductive reactance of the resistor winding and the
> enameled wire winding will cancel each other. With some care and
> measuring gear the remaining reactance could be very low. The assembly
> would then behave almost as a pure resistance.
>
> Of course, care should be taken not to reach too high temperatures,
> because the enameled wire would then be damaged.
>
> Also, the added winding should be wound in the appropriate diraction (
> CW or CCW depending of the winding direction of the resistive wire)
> otherwise the two inductances would add instead ao canceling each other.
>
> Has anyone alredy tried this?
>
> 73
>
> Angel Vilaseca HB9SLV
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