Extracoils
Thanks for that dR Green.
I have built a couple of extra coils, each with different wire, wire lengths, spacing or some other variable. Once I find the one I’m happy with together with its terminal capacitance, I’ll duplicate it for the second (image) or receiving coil. So the answer is yeah but only for one coil thus far, not both together at the same time at the moment. The Extra coil does add to the output. I do look forward to having the two extra coils in place. I could try two different extra coils on each coil and attempt to tune to the same frequency by adjusting the top terminal capacitance. – Something I could try fairly soon.
The method of construction on the extra coils is I’ve been using half inch Teflon rod or wooden dowel as the spokes (salvaged Teflon rod, or baked wood dowel at 105C for several hours). The wire is space wound with the nearest desired diameter of fishing line. Then the windings, wire and fishing line against the Teflon or wood are painted with several coats of polyurethane. Once dry the fishing line is carefully removed and the wire holds its position, (hopefully, most of the time).
Here’s a little discovery tip: On some other trial builds the use of a white or clear ‘Silicon Tape’ is used between the spokes and the wire. This silicon tape acts as a nice ‘roadbed’ for the wire. As it has some springiness, spongy quality to it, as well as a good insulator. It provides some tension and helps hold the wire in its location when space wound, polyurethane is then not required, neither is cutting slots – Likely this is the standard method I’ll use in future.
As push-pull transmitters are difficult to impedance match (Pi-networks not recommended or used for push pull). I’ve also been working on an add-on module for my existing single ended transmitter, as I have an 833a tube and its filament transformer to extract out of an old sparking VTTC I made years ago.. Then I can use a beefed up Pi-network to Z match.
This and some sort of modulation would be nice.
Originally posted by dR-Green
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I have built a couple of extra coils, each with different wire, wire lengths, spacing or some other variable. Once I find the one I’m happy with together with its terminal capacitance, I’ll duplicate it for the second (image) or receiving coil. So the answer is yeah but only for one coil thus far, not both together at the same time at the moment. The Extra coil does add to the output. I do look forward to having the two extra coils in place. I could try two different extra coils on each coil and attempt to tune to the same frequency by adjusting the top terminal capacitance. – Something I could try fairly soon.
The method of construction on the extra coils is I’ve been using half inch Teflon rod or wooden dowel as the spokes (salvaged Teflon rod, or baked wood dowel at 105C for several hours). The wire is space wound with the nearest desired diameter of fishing line. Then the windings, wire and fishing line against the Teflon or wood are painted with several coats of polyurethane. Once dry the fishing line is carefully removed and the wire holds its position, (hopefully, most of the time).
Here’s a little discovery tip: On some other trial builds the use of a white or clear ‘Silicon Tape’ is used between the spokes and the wire. This silicon tape acts as a nice ‘roadbed’ for the wire. As it has some springiness, spongy quality to it, as well as a good insulator. It provides some tension and helps hold the wire in its location when space wound, polyurethane is then not required, neither is cutting slots – Likely this is the standard method I’ll use in future.
As push-pull transmitters are difficult to impedance match (Pi-networks not recommended or used for push pull). I’ve also been working on an add-on module for my existing single ended transmitter, as I have an 833a tube and its filament transformer to extract out of an old sparking VTTC I made years ago.. Then I can use a beefed up Pi-network to Z match.
This and some sort of modulation would be nice.
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