Neighborhood radio in Half Moon Bay

About a year ago I was in Half Moon Bay driving to and from a conference when my ears fell on KHMB, a noncommercial low power FM (LPFM) station on 100.9 fm. It was playing oldies interrupted by local public service announcements, some of which sounded like ads, all apparently automated. what mattered was that it sounded very real and local. I like that.

Some digging revealed that it is licensed as KHMV-LP, but called “KHMB AM and FM” on the air. (I suppose their callsign is KHMV because KHMB is already taken by a station in Hamburg, Arkansas.) It’s also “AM and FM,” since it radiates on 1710am as well. In fact, many of the announcements only mention the AM signal, though they are simulcast, at least when I was listening.

At first I thought the AM signal must be licensed as a TIS (Travelers Information Station). But, according to Wikipedia, “While 1710 kHz appears on many radios, it is unused even by TIS stations, exception being TIS (WQFG689) licensed with a waiver to the Hudson County, New Jersey. This is because aeronautical radio navigation may use 1708 kHz. It has also been a popular frequency with both Part 15 and North American MW pirate radio station operators especially in the Midwest and east coast of the United States.”

What little I know of the rules suggest to me at first that KFMB is either a pirate or operating under Part 15 of the FCC rules, which say, “On the standard AM broadcast band, transmission power is limited by 100 milliwatts of DC input power to the final RF stage (with restrictions on size, height and type of antenna).” That’s just one tenth of one watt. A licensed AM station would radiate using a tower, preferably one at least a quarter wavelength long. On 1710, that would be 141 feet.

I knew from its license that the KFMB FM transmitter is at 37° 26' 49" N, 122° 25' 55" W, which is on the south side of Wavecrest Road, off Highway 1, south of Half Moon Bay. I couldn’t find it when I went looking. Nor could I find anything that looked like a tower for the AM signal. Later, in correspondence with somebody who helped set up the station, I learned that the AM signal comes from a short whip antenna behind Cameron’s Pub at the corner of Highway 1 (Cabrillo Highway), and Wavecrest Road. (Here’s a Google Streetview.) The same guy also told me the transmitter is somehow compliant with FCC rules.

I kinda doubt it, because we got both signals clearly in our car for 25 miles along US1, losing them a short distance past Pescadero Beach. That’s what I would expect from the licensed FM signal, but awfully good for a 1/10th watt unlicensed signal radiating from a whip antenna just a fraction of the ideal length. True, even a whip antenna can be tuned, AM signals love salt water, and there’s a lot of it between the transmitter and points south along the highway. But still, I would have guessed the station was at least a few dozen watts.

But hey: no harm, no foul. There is absolutely nothing else on 1710, far as I know. So, rock on.

On the Net, of course, coverage is worldwide. You can get the stream at https://player.live365.com/a48254, as well as in a window on the station website. Check it out. It’s great local radio.

[Follow-up on March 16, 2021: The station is still there online and apparently thriving. It has a different stream source, so I edited the above to correct that. Meanwhile I have also tried to pick up the AM signal when I’ve been in the Bay Area and traveling down the Peninsula on Interstate 280—and have been amazed to find it there. Faint, but there. This is remarkable for a Part 15 signal, I must say. ;-) ]

This post was originally published at doc.blog on October 29, 2016. I republished and updated it here because Google doesn’t find the original. Bing does.

Author of The Intention Economy, co-author of The Cluetrain Manifesto, Fellow of CITS at UCSB, alumnus Fellow of the Berkman Klein Center at Harvard.