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stuff [2023/12/15 18:12]
admin 		stuff [2025/02/03 17:10] (current)
me
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  reading back to post #1, I see you said you would like to tune the longwave band. Well, as we found when adding capacitors it's the square of the capacitor to halve the frequency. The same works for increasing the inductance to lower the frequency so in theory if we wanted the halve the low end frequency from 500kHz to 250kHz we would have quadruple the number of turns,not double. BUT there is something working in your favour for a change. The formula for inductors in series is "Lt=L1 + L2 + 2M" where "M" is the coupling between the two coils. Also in post #1 you said you had wound on 120 turns - here's what I suggest - find a turn in the middle of your coil, say turn #60. put a turn of tape either side of turn 60. Carefully, snip that turn and unwind turn 59 and 61 and twist the two ends together. If you're lucky, the insulation of the wire should be burnt off with the heat of your soldering iron, if not you'll have to sandpaper some of the insulation off - then solder the two ends together. As your two coils are almost 100% coupled via the ferrite rod then you might only need to double the number of turns. Now this 'tap' you have made should be one connection for the coil for the AM BC band, and the far end should do for the LW band. You may have to search around for a station or find some way of generating a signal. Just make sure the AM BC band works before getting too involved with the LW band.  reading back to post #1, I see you said you would like to tune the longwave band. Well, as we found when adding capacitors it's the square of the capacitor to halve the frequency. The same works for increasing the inductance to lower the frequency so in theory if we wanted the halve the low end frequency from 500kHz to 250kHz we would have quadruple the number of turns,not double. BUT there is something working in your favour for a change. The formula for inductors in series is "Lt=L1 + L2 + 2M" where "M" is the coupling between the two coils. Also in post #1 you said you had wound on 120 turns - here's what I suggest - find a turn in the middle of your coil, say turn #60. put a turn of tape either side of turn 60. Carefully, snip that turn and unwind turn 59 and 61 and twist the two ends together. If you're lucky, the insulation of the wire should be burnt off with the heat of your soldering iron, if not you'll have to sandpaper some of the insulation off - then solder the two ends together. As your two coils are almost 100% coupled via the ferrite rod then you might only need to double the number of turns. Now this 'tap' you have made should be one connection for the coil for the AM BC band, and the far end should do for the LW band. You may have to search around for a station or find some way of generating a signal. Just make sure the AM BC band works before getting too involved with the LW band.
  
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stuff.txt ยท Last modified: 2025/02/03 17:10 by me

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