DEE-cal is the only way I’ve ever heard it. I grew up in northern NY near Quebec.
The first time I heard it pronounced “deck-al” was an episode of Corner Gas.
I’ve been putting together models off and on for the last 37 years, and it was only this year that i heard someone pronounce it deck-al. It sounded odd to my ears, but I just assumed it was a British thing.
Only ever heard DEE-cal. NYC and surrounding area.
You can probably tell what my hobbies are. 
This thread reminds me of the time I drove through the pasture and got some feckle matter on my veckle.
If you wash it off quick enough, it won’t get inflected.
Only if you pronounce “fuck all” like “fecal.”
… might not really be able to broach this with layman’s terms. I can’t tell what “hard k” and “little k” signify. No worries – just curiosity on my part.
Or as in the Irish “feck oil”
Yeah, they’re exactly the same “k” in all pronunciations. It’s the vowels and stress that change.
I’ve only ever said or heard Dee-kal.
Next you’ll tell me there are different pronunciations for coffee without caffeine (Dee-calf)
Ugh. In the Hitchcock movie Marnie, Tippi Hedron says “Pih-KHAN pie” about a million times. In that early-sixties Holywood style of overenunciation, it’s unbearable (IMHO). I don’t even like the damn dessert, but it’ll always be “PEEK-an” to me.
Actually, the second syllable is emphasized enough that the first syllable can get a little muted and the difference between “dee-” and “deh-” might be too subtle to detect.
My hearing is changing as I age. I don’t notice subtle changes in pronunciation anymore. Unless I’m listening for a difference.
I appreciate Webster providing audio pronunciation. It’s helpful to check that I’m pronouncing a word correctly.
Having mixed with hobbyists from down south, I have become used to switching from my usual Deck-all to the American Dee-cal. Although whenever I hear it, it sounds in my mind like:
“Yeee haw! How Y’all Doin’? Me an the boys are gonna put on some of these here Deeee cals, and then we’re fixing to have some barbeee que!”
Deee-kal, the same way Deee-Lite of “Groove Is in the Heart” fame is pronounced.
Dee-cal, with the emphasis on the first syllable.
You and me against the world!