Re: Parallel Resistance calculator
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From: main@4SQRP.groups.io [mailto:main@4SQRP.groups.io]
On Behalf Of John T. Fitzer
Sent: Thursday, June 21, 2018 8:19 AM
To: main@4SQRP.groups.io; kennick@...
Subject: Re: [4SQRP] Parallel Resistance calculator
Regarding the dummy load idea, Back in the days when I was running QRO (100) watts, I made a dummy load by immersing 20 1Kohm 2 watt carbon resistors in a quart of mineral oil with a SO239 mounted to the top of the can lid. From a practical
point of view, and without getting too deep into thermodynamics it is safe to assume that as a rule of thumb, any resistor immersed in oil will increase its dissipation capabilities by a factor of 4. So theoretically my red neck dummy load should be able to
handle 160 watts. I never tested it at that power level, but as I remember it never even got warm at 100 watts. Keep in mind I never held the key down for more the a minute or so. I was more concerned about killing the 6146’s.
Or you could immerse them in oil and make a unique dummy load
"Quis custodiet ipsos custodes?”
On Jun 20, 2018, at 20:45, Nick Kennedy <kennnick@...> wrote:
This reminds me of an article in QST in July 1963 called "Euclid and a quart of resistors". It showed how to take a quantity of resistors of a single value (say you have a quart of 47 ohm, 1% resistors ...) and combine them to produce any
I guess I'm regressing to my youth because I looked up that 55 year old article and ran though a couple examples to see that it worked. I don't think it really has much practical value - it's just an interesting demonstration of a technique.
On Wed, Jun 20, 2018 at 2:45 PM WA0ITP <wa0itp@...> wrote:
A while back someone posted, on some list, a link to a calculator that provided abt 15 or so parallel resistor combination which matched a desired value that was entered into the calculator. Matching parallel
values were tabulated as were error deviations in percent. Alas I lost the email with the link.
Google is not my friend on this. Did anyone here see and save that email/link? Thanks for checking, appreciate it.
I love this radio stuff.
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