[Lowfer] 8 kHz VLF loading coil idea

[Ed Phillips]

Bill Ashlock wrote:
> 
> Hi Ed,
> 
> You say: "A Q of 100 (for the loading coil) sounds too low by orders of
> magnitude!"
> 
> The system Q, meaning the combined Q of the coil, the top hat (along with
> all the tree losses), and the ground, is seldom better than 50 on most
> Lowfer antennas despite the fact that some go hog-wide in designing loading
> coils with incredibly high Qs. A lowfer loading coil having 3.5mh and Q of
> 500 has an effective series resistance of 7 ohms at 160kHz. The same loading
> coil having a Q of 100 would have a series resistance of 35. If the ground
> resistance is 35 ohms and the tree loss is 8 ohms, the radiation power gain
> in going to the better coil would be the ratio of the two total system
> resistances. That's 50 ohms compared to 78 ohms. This is 1.56x or 1.93 db -
> hardly detectable in a normal receiving situation. Due to the extremely low
> reactance of the top hat at 9K, and the huge inductance needed to resonate
> this, a Q of 100 in a coil this big would be all one could hope for. And if
> one could, in fact, gain 1.93 db by a better coil, it would be a whole lot
> simpler to just multiply the power input by 1.56X.
> 
> What do you think?......
> 
> Bill

	Under your conditions I agree completely, particularly about those who
go to fantastic lengths to make really high Q loading coils without
considering the other losses in their system.  For instance, the
effective resistance of my 180 kHz antenna system is about 25 ohms,
mostly ground resistance.  When the antenna was surrounded by some large
live oak trees (unfortunately dead of oak tree root fungus) the
resistance was between 35 and 40 ohms depending on the wetness of the
leaves (and of the base insulators).  As for your last statement I also
agree, just as I wonder whether a signal increase by 1.9 dB is really
perceptible in the presence of all sorts of man-made interference and
propagation variations.  You could measure it easily enough on an
antenna range but I suspect that in A/B over the air tests it would be
hard to tell which was which.

Ed

P.S.  In spite of all that I like high Q coils for their intrinsic
properties, whether the do any good or not.