A FULL Wavelength on 40M is 140 ft.
A HALF WAVE Dipole is 66 ft allowing ~5% for end effects.
A 47 ft boom is .335 WL. The square root is .58 sq rt WL
(whatever the ***? those units represent). If we accept that
the units should be WL, that corresponds to 81 ft which is
close to optimum. Actually, stacked 2L40's exhibit peak
gain when stacked at 80 and 160 ft.
On Sat, 28 Jul 2001 16:18:19 +0000 alsopb <firstname.lastname@example.org> writes:
> As stated originally the boom length in the formula is in
> A 47' boom is about .7 wavelength on 40 meters. The formula
> a spacing of .84 wavelenth or about 56 feet.
> Tom Rauch wrote:
> > Hi Brian,
> > I don't understand what the following means. Is something wrong?
> > > I queries WX0B about the rule of thumb regarding "optimum"
> > > height.
> > >
> > > Here was his response:
> > > ***********************************
> > > For HF antennas over ground, W2PV did the math correctly and the
> > > formula is SQ rt of boom length is the widest stacking distance
> > > should use on a yagi. The results are in boom lengths just as
> > > state.
> > My 40 meter yagi has a 47 foot boom. Optimum stacking distance
> > for gain is ~90 feet, depending on array mean height.
> > Using that formula, I should stack my 40 meter beams sqrt of 47,
> > or 7 feet apart MAXIMUM?? A 1 WL boom antenna would stack
> > at .7WL...which also would be much less than optimum
> > ....although getting closer.
> > Was something stated or conveyed incorrectly above, or is
> > something missing? It clearly is not correct.
> > 73, Tom W8JI
> > W8JI@contesting.com
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