A Slinky is so much like a Helical Antenna that it seems to be the same, and a Helical Antenna is like an Air Core Inductor Coil which, if used with a Vertical Antenna would resemble a loading coil. I have watched many Utube videos and none of them clearly distinguish these various types. And so I turn to you, the Part 15 Members, to provide clarity.
Time has gone by and no one has had anything to say about the antenna questions I posed. That's a problem here at the Part15 Official Website, failure to offer electronic information within a hobby comprised largely of electronic physics.
Today I watched some Utube videos about Delta antennas, another interesting design, but most of their discussion pertained to higher frequency shortwave and doesn't apply to the lowly Part15 medium wave band.
What I may end up doing is to sign up for a radio engineering course at the nearby community college. Then I could come back here and do what a previous forum member did: strut and crow about how smart I am as an RF Engineer. It would be far easier if you were the one to attend the school while I wait here until you return.
Not being that knowledgeable about this I can give an opinion and have to say that a slinky which is a toy for those that don't know that is a large spring about 3 inches in diameter and maybe 3 or 4 inches long compressed that can go down a stairway by itself turning head over heels and other tricks. It is very flexible.
Using this as a coil for a loading coil on an AM antenna wouldn't work as there is no insulation to prevent electrical shorting on the steel between coils/windings, not to mention getting the correct inductor value.
Here's a slinky
https://www.partycity.ca/en/pdp/slinky-original-metal-classic-spring-toy-for-adults-kids-ages-5-0504983p.html