Dear J, LF Group,
I would certainly go for the simple solenoid initially - it is much easier
to make, and also to alter the inductance via tapping points, which is
usually necessary when setting the system up.
Also, "highest Q" is not necessarily "best" for a transmitting antenna
loading coil. You must also consider the effects of heating, and insulation
breakdown, which will often be worse with a multi-layer winding compared to
a solenoid, due to packing more turns together. Q is not a strong function
of the physical dimensions, so you usually need a drastic increase in size
to make a big improvement to the Q. The overall system improvement possible
by going from a reasonably good loading coil to a really high-Q loading coil
is usually less than 1dB, which is small compared to what can often be
achieved by modifying the antenna slightly.
My suggestion would be to wind a solenoid using the largest diameter former
and thickest wire you have available, with plenty of tapping points and not
worrying too much about the geometry of the coil. Once the system is
working, you will be able to evaluate the losses in the coil and antenna,
and decide if it is worthwhile making a better loading coil.
Cheers, Jim Moritz
73 de M0BMU
|
