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Resistor polyhedra

Dear Reader,

Those of you who want to work out your brains might be interested in the resistor polyhedra contest article which I wrote for RadCom. This has been designed to be a challenge which will both tax the minds of very bright people with years of experience in physics / electronics and also offer the new commer some easier problems to allow them to get their feet wet.

I have made a lot of funny networks out of 1000 ohm metal film resistors, my trusty 25 W Antex iron has been very handy for this task. I tend to like to use a iron jacketed 25 W Antex iron for most soldering work. I bought the Antex back in 1992 and it is still going strong. I used to use a 25 W Weller (from the late 1980s) with a copper tip but I found that that the tips were dissolving in the solder too much for my liking. I have to confess that I worked a lot with the Weller, the Weller had coated tips but they did slowly age and dissolve. So what I used to do with that iron was to use 1970s solid copper tips from another older iron I used to own as a lad. I used to have to file the copper tips once in a while to get the shape right.

I have found that a 50 W temperture controlled Weller with a modern tip to be a nice iron. I think that it is a better iron for large items than the 25 W Antex. But I think if you want the best value for money the 25 W Antex is hard to beat. I used that in my youth to build quite a few things.

RadCom is the magazine of the RSGB (Radio Society of Great Britain). Sadly due to an error in the production process it did not publish a closing date. The closing date is 08:30 GMT on the 7th of Jan 2019. To have a chance an entry must have reached the RadCom office by that time / date.

The contest is in RadCom in the december issue at around page 40

The rules by which I will be judging the contest are

Rule 1.

If one person has calculated or measured correctly more networks than any other person, then this person shall be the winner. Any person who gets within 2 % of the correct value will be judged to have got it correct. The networks made by Mark Foreman are to be used to referee what the correct values of the networks are. If the RadCom office or other RSGB workers were to create their own versions of the networks then the average of the values measured from the networks will be used.

Rule 2.

If under rule 1 no single winner can be identified, then Mark Foreman will judge the method used to determine the values of the networks. Mark Foreman normally favers methods which use the bare minimum of advanced mathematics. Thus if the solution requires exotic things like Laplace transformations, matrix operations and the like he will disfavour. Mark Foreman reserves the right to consult other people when judging methods which use advanced maths.

Rule 3.

If under rules 1 and 2 no single winner can be identified, then the first most correct and elegant answer to arrive at the radcom office will be the winner.

Rule 4.

If under rules 1, 2 and 3 no single winner can be identified, then the winner will be randomly selected. The possible winners will be assigned numbers such as 1, 2, 3 and 4. Then Mark will use a measurement of the background radiation in his office or lab as a random number generator. The least significant digit in the total count numbers (number of events detected) will be used to decide the winner.


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