If you’ve ever dial-hopped and stumbled across a poet reading her latest haiku, followed by an ancient cylinder recording of a singer from the very early 1900s, chased by an extended bebop jazz jam and rounded-off by by a live singing harpist, you’ve discovered a broadcast relic of the ’60s, “free form radio.”

It’s a non-corporate, non-network “listener supported” “community” station, as opposed to a member of the NPR network. It’s radio for “people who don’t quite fit in.” And it’s a rare thing.

You can find such typically low-power (limited reach) stations in big cities, in the mountains of Virginia, Tennessee and North Carolina, in college towns such as Madison, Wisconsin or Winter Park, Florida. And perhaps the most famous survivor of the species is WFMU-FM in Orange, New Jersey, just across the river from Manhattan.

“Sex and Broadcasting” is the title of a famous “how to” book by Lorenzo W. Milam about getting such a station licensed, staffed (volunteers) and on the air. It’s also the title of a lively and engaging documentary about WFMU’s history and struggles to stay solvent and relevant in the age of Internet Radio and a million other distractions for this station’s metro-New York audience.

Tim Smith’s movie follows station manager and guiding light Ken Freedman as he pulls his own on-air stunts, doing a “meet up with our listeners” live in the middle of a local lake (from a canoe), leads the camera through the cluttered archives, record and CD stacks and arcane music reproduction gear (the aforementioned Edison cylinder player) and tries to rally the independent thinkers there to fund raise to pay their bills and expand their signal reach into NYC.

WFMU, which started life as an Upsala College FM station (Upsala closed, the station lives on), is captured at a fun, desperate moment in its history. There were popular hosts, popular programs, including “JM, The Jewish Moment,” a daily dose of ethnicity and ardent Zionism, the beehive of studios and stacks filled with comics, musicians, hangers-on and ardent believers in this sort of radio, all there for one of the station’s near-death experiences — drowning in debt.

Considering the history of such stations, it’s hardly surprising that the volunteers are generally older, whiter, more Jewish (in this station’s case). They are aged hippies and assorted other eccentrics. Decades of donated labor hosting shows have made them polished presenters, people capable of genuine novelty on the air. Their personas and programming zaniness have made them frequent subjects of profiles in the other New York media.

The station had one host set the record for one person being continuously on the air, makes live performances of every manner of music (much of it unpolished) and has an internet presence that created a worldwide web audience for its weirdness, which makes fundraising easier.

“Community” stations aren’t just licensed to serve their community, they create their own community — of supporters, volunteers, listeners and call-in show guests. And WFMU, like such stations I’ve appeared on, volunteered for and just listened to — WORT, WUVT, WPRK, WDVX, etc. — excels at this, which Smith’s movie notices but doesn’t dig into.

While hosts and former hosts talk on camera, a bit broader picture of the station’s whole eco-system would have made a better movie (and a longer one, alas). The only fans who speak on camera are famous — Adam “Ad Roc” Horowitz of The Beastie Boys, comic Patton Oswalt, “Simpsons” creator Matt Groening.

And nothing Smith shows us here can convince the viewer that this brand of broadcasting might stage a comeback, any more than any other terrestrial broadcasting medium. Thus, it’s an exercise in nostalgia.

But “Sex and Broadcasting” is still a fascinating block of broadcasting trapped in amber, a little radio history about passionate people doing something they love, willing to beg for bucks on the air to continue doing it and finding enough kindred spirits, “people who don’t quite fit in” in a shrinking sea of radio listeners to cling to FM life a little longer.

MPAA Rating: unrated, profanity

Cast: Ken Freedman, Matt Groenig, Adam “Ad Roc” Horowitz, Tom Scharpling, Patton Oswalt

Credits:Directed by Tim K. Smith. A Netflix release.

Running time: 1:18