Crystal Radios Are Still For Sale

It's hard to argue that radio as a hobby and as an industry aren't in decline. But I do my best. My latest canary in the coal mine is the toy crystal radio set. You remember the kit: 1 diode, 1 tuning rod, 2 connecting wires, 1 copper wire coil, 1 earphone and maybe a cardboard tube.. maybe some rubber bands and a tuner so some kind; or maybe not. They still make that kit... many different companies do actually. See below.

Makes and models range from hardwood mounted toys clearly intended for adults to flimsy designs made mostly of paper. The difficult level clearly varies, but not one of these costs more than $25, so they fall into the toy category.

Science Store - Crystal Radio Kit
 https://store.sciencebuddies.org/Elec_p014/COM-0001-KIT/Crystal-Radio-Kit.aspx

Poof-Slinky - Crystal Radio Mini Lab
http://poof-slinky.com/product/crystal-radio-mini-lab/

Maxitronix - Crystal Radio Kit
http://www.elenco.com/search/searchdetails/crystal_radio_kit=Mjc5

Modern Radio Labs - No 2 Crystal Radio Kit
http://www.modernradiolabs.com/MRL%20No%202%20Crystal%20Radio%20Kit.htm

Peebles - PO-002 Crystal Radio Kit, With a Cylinder Coil
http://www.peeblesoriginals.com/catalog/45.php

Go Labs - Build Your Own Working Crystal Radio Lab Kit
http://www.amazon.com/Build-Your-Working-Crystal-Radio/dp/B000EMB8AA

Xtal Set Society - XS-OB1 Oat Box Radio - Pack 1
http://www.midnightscience.com/kits.html

Flights of Fancy - Crystal Radio Receiver
http://www.crafts4kids.co.uk/flights-of-fancy-radio-receiver/p1310

Artec Build Your Own Crystal Radio Science Craft
https://www.virtuabotix.com/product/artec-build-crystal-radio-science-craft/