Henry Kiefer wrote:
and that takes a lot of ampere
turns. You can deliver more ampere turns to the rod than
your transmitter output can deliver if you resonate the coil
with a capacitor. That way, you have the current bouncing
back and forth through the capacitor added to the current
from the amplifier. If the coil-capacitor Q is, say, 100,
there will be 100 times more current through the coil than
the transmitter is delivering. This will probably take a
coil with a considerable mass of copper in it.

John, that is what I have seen! I resonated the antenna coil and driven it
with it's resonance frequency. Seems that the achievable distance was a
little more than the circuit without resonating capacitor.

You say, that driving the ferrite rod into saturation will force it to leave
more power into air? Why?

You misunderstood what I said. It was, " the most field you can
generate with the ferrite rod antenna will occur when it is
almost reaching saturation,"

If you saturate the rod, the field you generate will have lotsof 3rd
harmonic components in it, but little more of the fundamental. I was
trying to emphasize that you will need as strong a magnitic field as
possible aat the transmitting antenna, and just below saturation is
that limit, when a ferrite core is involved.

If the rod has a large lenght to diameter ratio (say , above 10) then I
think the uptimum coil arrangement on the rod also doffers considerably
for the transmitting and receiving cases, since the receiving case does
not deal with saturation.

In the receiving case, the end sections of the rod act as flux
collectors, and only the middle thirs or so has almost all the
collected flux passing through it, so this third is the optimum place
for the coil. /in the transmitting case, the rod has a tendency to
saturate at the center, first, with this arrangement, and you want
essentially the whole rod to approach satuation at the same ampere
turns. This will produce a field that acts as if it has been produced
by the full length of the rod. You can achieve something close ot this
by spreading the turns out, all over the rod, with an extra
concentration (a second or third layer layer, perhaps) at the ends.
Something like this (shown in cross section. View with fixed width
font i.e. Courier, so charcters are on grid pattern):

* = wire in cross section
# = rod

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