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Author Topic: QUESTION: Johnson Matchbox primary coil wiring  (Read 2828 times)
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David, K3TUE
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« on: March 12, 2007, 11:26:48 PM »

I got one of these on eBay and opened it up.  The mods in it appear to be minor.  One I thought there was was the input was connected to the coil at the first or second turn of 5 or 6.  This appeared wrong.  I knew I should have asked, but I went ahead and changed it.  I moved it to the last turn based on the fact that I had read K1JJ's description of his super-tuner which has 4 turns on the primary.  But now I look at the Matchbox schematic and see that the primary input is tapped at the second turn, just like it was.

The question is, should I bother to put it back, or will it work fine as it is.  And if it will work fine, how have I changed it's operating characteristics?
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David, K3TUE
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« Reply #1 on: March 13, 2007, 11:45:42 AM »

David,

If you look at the manual, it's on BAMA if you don't have one, from the factory the power input is tapped at the 50 ohm position on the coil, the receiver is tapped at the 300 ohm position. Kinda easy to see old solder points if the taps were moved in the past. This info is from memory and on the KW matchbox.

73's
wd8kdg
Craig
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WA1GFZ
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« Reply #2 on: March 13, 2007, 12:44:51 PM »

Changing the tap changes the tuning range. I've never moved mine but remember the manual will tell you what changing the tap does to the tuning range. I think it shifts the range down if I recall.
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