Shadow300

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The formula for calculating the receiver coil is found with Figure 8. For the transmit coil, use Figure 5. The transistor in the TX circuit affects the outcome but you can ignore its effects because the TX power is very high and when the transistor is going on and off, the resistance is going up and down. Use 16khz as the frequency for your calculations.

Once you solve for the inductance value, you can decide on what kind of wire to use so you can wind your own coil. This electronics stuff may look like it's the same as building a model airplane but it's really not that simple. You don't just put the bits together and they work. In this case, the 1980 article left out the value of each coil and the construction details for the coils. They may have been in a subsequent issue as errata but it's too long ago now to find out.

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http://www.thunting.com/smf/index.php/topic,18350.msg118920.html#msg118920

		Quote:			Posted by flamecrusader
	Uhm...I'm sorry but what is the value of capacitance & resistance for the shadow MD?and how do i calculate the number of turn needed?The only thing that I have is the frequency right? Sorry but I'm actually a bit weak at electronics(and my professor still insists on me making the MD... )...Thanks again...

What course are you taking where your professor insists that you build something of which you are not capable of building?

I gave you a link to all you need. Aside from me doing the math, it's all perfectly presented for you. So here's the deal. You don't need a capacitor or a resistor for making your coil. You need wire. The wire gauge, number of turns in the coil are all something you choose after you calculate the coil's theoretical inductance. The coil's inductance is calculated from the resistance already defined in the circuit, and the capacitance, already defined in the circuit. The configuration of the circuits is different for the Rx and Tx so you have to match the circuits as I told you. Then use the matching formula. Plug in the values and you will have your Rx and Tx coil. It's a math problem.

Now if the problem is that you don't know what the schematic symbols are for the resistors and capacitors and can't read the two circuits in question, then you are in the wrong place and taking the wrong course under the wrong professor.

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http://www.thunting.com/smf/index.php/topic,18350.msg119091.html#msg119091

Well, old buddy, if you want to do the math for him, I'll loan you my slide rule. Remember those? Never need batteries? Last forever in a land fill? Very high precision and 100 times faster in the right hands than a modern Cray computer.

The magazine article is probably incomplete. There are other factors like the coil phase relationship between the Tx and Rx that need to be known. The article is very old and probably the details are lost forever now.

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