Decades ago I built a load with two100 Ohm, 200W size glass resistors. It
worked well to 6M after using a mica trimmer to cancel the small reactance,
measuring and replacing with a larger fixed mica.
They were placed in a metal can and filled 3/4 of the way up in good old
tasty PCB's courtesy of a utility company road crew.
Carl
KM1H
----- Original Message -----
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
To: "Vic K2VCO" <k2vco.vic@gmail.com>; <amps@contesting.com>
Sent: Monday, February 06, 2012 1:47 AM
Subject: Re: [Amps] reducing the reactance of a wirewound resistor
>I had some 600 ohm Non-inductive wire would glass covered resistors a long
>time ago.
> Dropped one and broke the outer glass covering and could see the wires on
> the center
> ceramic center. There were 4 wires 2 wound C.W. and 2 wound C.C.W. with
> no insulation.
> They made a neat cross hatch pattern on the ceramic cylinder.
> They could have functioned two ways. One was a close simulation of a
> cylinder of resistive material if each cross connection actually made a
> good connection.
> The other is that the magentic fields would cancel out. Possibly a
> combination.
>
> 73
> Bill wa4lav
>
> ________________________________________
> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf
> Of Vic K2VCO [k2vco.vic@gmail.com]
> Sent: Sunday, February 05, 2012 7:01 PM
> To: amps@contesting.com
> Subject: Re: [Amps] reducing the reactance of a wirewound resistor
>
> What HB9SLV suggested was not exactly an Aryton-Perry winding, although
> the principle is
> the same. Instead of being in parallel, his idea had the windings in
> series. So they will
> always carry the same current!
>
> On 2/5/2012 9:23 AM, jeff millar wrote:
>> 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
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
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