I listen to quite a lot of the UFO/paranormal internet media, including Coast to Coast, The Paracast and Dreamland and have noticed that there is a real confusion sometimes among guests and presenters about when to say phenomenon, rather than phenomena.
Now I suppose it’s risking appearing snarky by pointing out the difference here as I only have third form Greek (I gave up after my teacher shouted at me for not learning the Greek capital letters) but my motivation is pure: some of the speakers on these shows are well-educated and are trying to make a case for the scientific investigation of UFO’s, bringing the subject out of the world of tabloid ridicule, because frankly, there is a genuine phenomenon of potentially paradigm-shaking importance that deserves serious investigation. And I’m right behind them.
If the serious researchers behind this movement want to be taken seriously, they’ll need a command of English up there with the best of those they are trying to convince. If they don’t know the difference between phenomenon and phenomena (both words they are going to be using a lot), they risk losing credibility in their first sentence.
It’s very simple: phenomena is the plural of phenomenon. Thus:
One phenomenon.
Twenty-seven phenomena.
It’s the same rule with criterion, by the way.
Monnow Man 
Well, we certainly have the same listening habits, and although you are correct, I’d say there are bigger problems relating to content here. But in terms of broadcasting, Gene Steinberg of the Paracast gets my vote for the most professional, clear and measured speaking voice.
Content is tricky because there aren’t enough quality guests to go around all the shows, especially C2C which has to find someone every night. Inevitably the quality is going to suffer and I sometimes wonder if these shows would do us all a service by improving quality by reducing quantity.