....[snip]....
The hardest part of making a choke balun is obtaining the ferrite ring....

Use a TV-set flyback transformer core; see:
"another balun design", by Fred Brown, W6HPH, in Ham Radio magazine
of May, 1982, pp. 54-57

"Three Baluns for a Buck" by Donald E. Lively, W6SJQ, from a magazine
which didn't print either its name or the date on the pages I saved!
but it basically says the same thing as the HR article.

A hint on p. 37 of the August, 1987, QST describes "The Baby-Bottle Balun",
an air-core balun based on DeMaw's article "Simple Coreless Baluns" (QST,
Oct. 1980, p. 47; which I apparently didn't appreciate enough to keep).
--
--Myron A. Calhoun.
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)