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Offline Pgill
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« Reply #30 on: August 08, 2012, 12:05:49 am »
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Now this is something I am learning about  Great only made crystal set radio coils  Funny

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God Bless
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Offline GoldDigger1950
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« Reply #31 on: August 08, 2012, 01:41:00 am »
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Quote:Posted by xavier
If you take a bad machine and place an excellent coil on it the chances are that you will end up with a fair machine or even a good machine.

There's no doubt that a good coil will improve a machine's performance but there are limits. As a blazing example, look at these folks trying to tow a gigantic coil behind them using an Ace 250 or some other portable machine. It just can't be done. The power required to drive that huge coil and push the magnetic field out there is just too much for that poor little box to handle. These guys all need to understand that a coil alone is not the answer. This is why every machine has a different coil. The machine is designed to match the coil and vice versa.

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It's all about that moment when metal that hasn't seen the light of day for generations frees itself from the soil and presents itself to me.
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« Reply #32 on: August 08, 2012, 03:18:12 am »
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Hi Xavier

You've probably already thought of this, but you can monitor the magnetic field your tuned circuit is producing by using a second (untuned) coil connected to a scope input, and looking at the voltage induced in it.  That would give you an unambiguous indication of what happens as you go from resonance to non-resonance.

Gwil


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Offline xavierTopic starter
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« Reply #33 on: August 08, 2012, 03:52:08 am »
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Yes I use that system on my PI machines when I want to see the power of the field produced by the coil and up to where I can go before things start to get hot. I have a frequency generator that I must take a look at as I want to use it in my experiment's too. If I recall I should also have an LC circuit that I build some time ago to test my coils (Never used it) all that I need to do is change the cap I'm just thinking now if I shouldn't use a tuning cap? I'd like to get the circuit in perfect (as close to) resonance to see the result on the coils field first.

Well GD all the machines that I have designed and build were build around the coil and I still failed horribly the first few times, but the first one that actually worked made it all worth while.   

Quote:Posted by GoldDigger1950
As a blazing example, look at these folks trying to tow a gigantic coil behind them using an Ace 250


 Grin Grin I remember that post but I guess that it's all part of the learning curve. One of my guys tried to jump start the tractor with the quad cost me R450 to replace the battery  Grin I laugh about it now but let me tell you that I was mad at the time. Ho and the tractor did start (Ford 6600) that's the worst part of it.
     

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« Reply #34 on: August 08, 2012, 04:11:11 am »
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Do you mean a tuning capacitor across the pickup coil?  I would definitely advise against it in this case.  You'd have two tuned circuits and both of them would be changing their behaviour as the frequency changed.  Strictly speaking an "untuned" coil has its own resonant frequency of course but if it is far enough away from the driving frequency its response will be pretty much constant, which keeps things simpler. 

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Offline xavierTopic starter
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« Reply #35 on: August 08, 2012, 07:01:01 am »
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No I was referring to the LC circuit which is build around a colpitts oscillator as the transmitter.   

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So many questions so little time

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« Reply #36 on: August 19, 2012, 02:57:28 pm »
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Just wondering if xavier had done any experimenting, and if so what the results were...

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Offline xavierTopic starter
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« Reply #37 on: August 20, 2012, 10:59:50 am »
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Quote:Posted by Gwil
Just wondering if xavier had done any experimenting, and if so what the results were...


I just haven't had the time yet.

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So many questions so little time

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