20m-EFHW for 40-30-20-17-15-12-10m

 40m EFHW resonates at 40-20-15-10m, but it’s 20 meters long, I think it’s too long for SOTA activations. I opt to a 20m EFHW which is about 10 meters. It resonates at 20m and 10m, to get 12-15-17m, I simply cut the wire and tune each band, form a linked wire EFHW. For 30m, I add ~10uH inductance at 17m joint; for 40m, I add ~20uH at 12m joint. I have tuned all bands(40-10m) below SWR 1.3:1 and the antenna performed well in the field.


The wire is from Ethernet cable twisted pair and the whole antenna weighs 1.5oz

For reference:

10m: 4.61m (15' 1-1/2") (not necessary, just in case)

12m: 5.15m (16' 10-3/4")

15m: 6.04m (19' 9-5/8")

17m: 7.22m (23' 8-1/8")

20m: 9.51m (31' 2-3/8)

30m: Add 10.7uH at 17m joint

40m: Add 20.3uH at 12m joint

The 49:1 transformer has 2T for primary and 14T for secondary.

Use 2m (6') coax, no tuner required for CW only operations.


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