Hyper-local radio in Half Moon Bay
by Doc Searls Saturday, October 29, 2016

I’m in Half Moon Bay, listening to KHMB, a noncommercial low power FM (LPFM) station here, on 100.9 fm. It’s playing oldies right now, interrupted by local public service announcements, some of which sound like ads, all apparently automated. It is licensed as KHMV-LP, but called “KHMB AM and FM” on the air. (I suppose their callsign is KHMV because KHMB was already taken by a station in Hamburg, Arkansas.) It’s also “AM and FM," since it also radiates on 1710am.

Many of the announcements only mention the AM signal, though they are simulcast, at least when I've been 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 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), or, alternatively, under 15.221, if the AM transmission originates on the campus of an educational institution, the transmission can theoretically be any power so long as it does not exceed the field strength limits stated in 15.209 at the perimeter of the campus..." In other words, too weak to get out of the yard.

The FM transmitter is at 37° 26' 49" N, 122° 25' 55" W, or somewhere on the south side of Wavecrest Road, off Highway 1, south of Half Moon Bay. I'm currently at the Ritz Carlton Hotel, about a mile away across a golf course, and the signal on 1710 is pretty strong. But the AM transmitter might not be in the same place as the FM, so I dunno. 

KHMB does stream, through http://khmbradio.com/player.html (also a window on its website), though not, apparently, though a published IP address. So, even though it's listed on TuneIn, you can't get it there.

[Update on Sunday, October 30...]

On my way out of town yesterday, I took a quick side trip down Wavecrest road to see if I could see either the FM or the AM antennas for KFMB. I didn't see an FM one, but, since the FCC license says it's only 15.5 meters (~50 feet) above the ground, it would be easy to miss amidst all the trees and industrial stuff there. But I did see, though some trees, a wire of unknown length that ended in an insulator. That, I suspect, is the AM antenna. (Those are normally vertical towers or poles, but horizontal will do too.)

We got both signals well in our car, driving driving south on US1 (Cabrillo Highway) to a short distance past Pescadero Beach. The signal path to that point, especially south of Tunitas Creek, is mostly over ocean. AM waves are favored by high ground conductivity, and salt water is best of all.

Hard to tell, but I suspect KHMB's AM signal is stronger than most—or possibly all—TIS signals, which (says the link above) "are limited to a 10 watt transmitter output power, an antenna height no greater than 15 meters (49.2 feet), and a coverage radius of 3 km." Since Pescadero Beach is about 15 miles from Half Moon Bay, I'm guessing that the station is putting out at a lot more than 100mw. But I dunno. 

[Later... in an email exchange, I found it operates under Part 15. So I'll take their word for it.]

Regardless of all that, give it a listen. It's great local radio.