I've added a feature to my coil inductance and Q calculator that can
help you evaluate a coil as a multiturn loop antenna. The program
calculates reception factor, a figure proportional to the signal voltage
a coil produces when resonated with a capacitor. You can experiment with
coil dimensions to see the effect on receive signal level. The program
can model circular, octagonal, hexagonal, or square solenoids that use
solid or Litz wire.
Originally I used the automatic optimizer that normally maximizes coil Q
to maximize reception factor. However, optimal coils turned out quite
long and used large amounts of wire. Reducing coil length by a large
factor often lowered performance only a dB or two. I'd never want to
build one of the optimal designs so I removed the optimization function.
It's easy to design a suitable receive loop by hand. Bigger is better,
but maximum diameter is limited by practical considerations. Wire size
is often determined by what's on hand or what's economical. That leaves
coil length and number of turns. You can vary each with the mouse wheel
and watch the reception factor change.
Reception factor is useful when you want to minimize reception. For
example, you can first optimize a 160m matching network coil for highest
Q and then adjust it to lower direct pickup. This might help maintain
deep nulls in a directional receiving array or minimize troublesome AM
broadcast signals.
Recently I greatly improved program accuracy for very short coils. I
also updated the skin effect and proximity loss calculations so they are
good down to DC. These changes increase accuracy for coils used as
low-frequency loop antennas, especially on the 2200m band.
Windows program:
http://ham-radio.com/k6sti/coil.zip
Reception factor reference:
https://rudys.typepad.com/files/coil-antennas-1919.pdf
Brian
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|