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#1
April 3rd 09, 03:51 PM
posted to rec.radio.amateur.antenna
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vertical antenna loading coil vs toroid
Cecil Moore wrote:
wrote: Did you ever try to model a resonator where the coil required is actually longer than the insulator, so that the vertical part of the resonator is actually inside the coil , ... Never modeled it but have seen its effects during 75m mobile shootouts. One fellow had a hamstick with the stinger bottom extending down into the hamstick loading coil. It was a very lossy condition which improved when he hack-sawed the excess stinger off. some times a hack saw *can* be a fine tuning tool. Do you have EZNEC? If so, I can modify a helical loading coil to extend the stinger into the middle of the coil and send the file to you. Conductors within the loading coil field lower the effective coil Q. However, I have had good luck with a 1.25" fiberglass pipe running through the center of the coil providing mechanical support. Perhaps you could consider swapping your insulator for a piece of fiberglass pipe or rod. Ahh, I had the idea of doing such a thing (add vertical travel) for my bugcatcher to fine tune swr if it needs tweaked a little. But it looks like I'll be hopping outside the car a lot after all. For 75/80 meters, I have like 4 separate taps. - 73 de Mike N3LI - |
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