Real Neighborhood Radio – On The Air

AM 1710 KHMBI was driving down the coast this weekend and stopped in Half Moon Bay for lunch. Around the town I noticed signs for “AM 1710 KHMB Radio” – naturally I tuned in. What I heard was a good signal, apparently locally programmed as well. I’d never heard of “KHMB” before and suspected it might not be a licensed station.

On the way out of town I continued to listen and noticed that station had a remarkably good signal even well away from the town center. This seems like incredibly good coverage, especially if the station was unlicensed.

When I got home I wanted to know more about the station, especially since it seems to be very similar to what I want to accomplish with Richmond Radio. I quickly found their website which presents itself as a truly local, commercial station.

A little research on the FCC database reveals no AM station with the assigned call letters KHMB and no AM station at all on any frequency licensed in Half Moon Bay.

An email to the station manager, Jim Henderson, confirmed that the station is operating as a legal unlicensed Part 15 operation, but with a twist.  KHMB uses five Hamilton Rangemaster transmitters with audio synchronization to provide 9 miles coverage along the coast.

The modulating audio is supplied by an Orban Optimod-9100, the classic Orban AM processor. This accounts for their very professional sound. I’d love to see some pictures of their studio, sounds like a fun station to operate.

My experience in hearing KHMB has me more seriously considering AM for Richmond Radio. My desired coverage area is much more modest than the 9 miles of town and country that AM 1710 serves in Half Moon Bay.  I may be able to cover the better part of the Inner Richmond with a single Part 15 AM signal.

I’ll have to save some money for the transmitter. I could build my own, but after all is said and done I would rather have some quality engineering pre-packaged for me. I would definitely roll my own if I didn’t have the physical constraints of transmission line, antenna, and ground system length placed on me by Part 15.

Also, I am wondering how I can leverage my Orban FM processor for use on AM. Obviously the stereo generator is of no use, but the compressor/limiter section might be applicable. The 8000 has left and right “test” RCA outputs from which I could get processed audio. These output would need to run through a de-emphasis network to undo the pre-emphasis applied for FM transmission.

I really like the classic Orban gear, so I will certainly be on the lookout for surplus AM audio processors. If you have one that you’re willing to part with, let me know.

The nice thing about Part 15 AM is that commercial operation is A-OK.  KHMB is run as a business, I like that. I would love to run ads for neighborhood businesses on Richmond Radio. Local businesses are a vital part of any neighborhood and should be supported by the residents.


One comment on “Real Neighborhood Radio – On The Air

  1. The only thing this operator is ignoring is that the regulations for Part 15 field strength for 1710 KHz as outlined in § 15.223 will allow for much less usable signal than what is allowed on the broadcast band as allowed under § 15.219. 1710 KHz is outside the defined AM broadcast band and shares its Part 15 field strength limits for 1705 KHz through 10 MHz.

    FCC regulations references are just a small portion of the available resources for those interested in legal, license-free low power radio broadcasting.

    Bill DeFelice

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