Chicago may be the home of the highest rated channel 6 TV station dressed in a radio station’s clothes.

I wrote about MeTV FM in February when it hit the airwaves. The station broadcasts on the audio channel of WRME-LP channel 6, which is receivable at 87.7 FM. I call these “back door” radio stations because they’re not actually licensed as such, and are heard on the FM dial because of a technological fluke, rather than by design.

MeTV FM is operated by Weigel Broadcasting, the company behind the nationwide nostalgia formatted television MeTV network seen primarily on HDTV sub-channels, playing a comparatively wide-ranging and eclectic selection of oldies targeted at a baby boomer audience. It’s been clear to me that the station hit a nerve because my post about it has received more than 40 comments, mostly from satisfied listeners.

According to media blogger Robert Feder the station has crept up to number 25 in the most recent Chicago ratings book. This gives the station a weekly cumulative listenership of 507,700 people, more than three times what the station had a year ago when Tribune Media operated it with a sports talk format.

Astonishingly, MeTV FM beats more established and well-known stations like ESPN Radio affiliate WMVP 1000 AM and conservative news-talk station WLS 890 AM. Keep in mind that this is a station that broadcasts with a fraction of the power of its competition, at a frequency that isn’t even an official part of the FM dial, and therefore isn’t receivable on all radios.

MeTV’s growing popularity only begs the question of how long the station will remain on its frequency, although its lease on life right now is up in the air. At some point in the future LPTV stations will be required to convert to digital transmissions, just like full-power stations did in 2009. This would mean channel 6 audio would no longer be received on FM radios.

September 1 of this year had been the mandatory digital transition deadline, but in April the FCC suspended it. The digital transition is probably inevitable, but not likely to occur until the upcoming television spectrum incentive auction is completed. LPTV stations have asked the FCC to permit them to stay analog, or even move into the actual FM dial, though these ideas aren’t popular with radio broadcasters.

Continued ratings success likely would give Weigel reason to pursue an actual FM signal, both to increase coverage area and keep it on the air longer. Although purchasing an existing FM license might be a bit expensive, there is probably a poorly performing station that could be leased.

Beyond it being a back-door FM station, MeTV FM is an interesting experiment, because by all accounts it’s a fresh take on an old format. It will be all the more fascinating if it can make the jump to a legitimate FM station.