I have tried to adjust the 30m coil on the HF2V in order to bring the resonance closer to 10.1 MHz. Increasing the length of the coild 17->20 cm did indeed move the cenntre frequency to 9.2 MHz, but going up to 25 cm did not seem to make a big difference; it only moved fc by about 250 kHz.
| L30 = 17 cm, fc = 8.97 MHz |
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| L30 = 20 cm, fc = 9.22 MHz |
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L30 = 25 cm, fc = 9.45 MHz
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| L30 = 32.7 cm, fc = 9.80 MHz |
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| L30 = 36.7 cm, fc = 9.95 MHz |
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This is just about the limit of how much the 30 meter coil can be streched, yet still far away from 10.1 MHz. I decided to go back to 26 cm and use the shorting strap instead.
| L30 = 26 cm, 1.5 turns shorted, fc = 9.77 MHz |
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| L30 = 26 cm, 2.5 turns shorted, fc = 10.08 MHz |
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| L30 = 26 cm, 5 turns shorted, fc = 10.86 MHz |
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So, it seems that L30 = 26 cm and 2.5 turns shorted is a good setting, fc=10.08 MHz and SWR better than 1.5 between 9.9 and 10.26 MHz. Now I can go on with the 40 meter coil.