[MRCA] Utility AM Modes

[Ray Fantini]

Man, you're old! I was in school in the seventies and remember from friends in the two-way business that the old marine AM service was cut off around 1973; they got lots of the old HF two-way radios as pull outs during retrofits. And I played around with some.
One of my favorite pack sets is the old USCG Sunair pack sets that was built right around that time that runs both AM or USB from 2 to 12 MHz, they always come with 2182 the old destress channel and 2166 that I assume must have been like channel 16 today.
I know I have worked you a couple times on 5357 running the Sunair before. Just finished installing ProgRpcks back before Gilbert for 5403.5 and am looking at setting it up for more channels when I get around to it. Have 3885 in it and was thinking of setting up 7296 . Fun radio although it is not real AM being they just insert a carrier on the USB signal for AM but works well.
Trivia! When I sat for my commercial license back in 76/77 I also took the Marine indorsement, and they still had questions on the old HF international distress frequency and how often you had to monitor it.

Ray F/KA3EKH


________________________________
From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on behalf of Michael St. Angelo via MRCA <mrca at mailman.qth.net>
Sent: Monday, October 19, 2026 10:18 AM
To: mrca at mailman.qth.net <mrca at mailman.qth.net>; milsurplus at mailman.qth.net <milsurplus at mailman.qth.net>
Subject: [MRCA] Utility AM Modes



While in college in the 1970's I had a job repairing 2 & 4 MHz AM Marine Radios. Most of the work involved matching the output to the fiberglass whip mounted on the boat. The Marine band was transiting from the MF/HF AM bands to the VHF FM bands so I advised the boater to invest in an FM set instead of fiddling with the AM set but few took my advice. Crystalized FM sets weren't inexpensive back in the days.

The FCC mandated transiting the Marine band and I believe other HF utility services to other modes. Does anyone know what the date of the transition?

I believe the HF Marine bands also had to transition to SSB mode. Did the Aeronautical HF bands have to transition form AM to SSB at that time? Were any other services affected?

Finally, the Marine SSB channels back then were spaced at 3.1kHz. Why was this odd channel spacing chosen? Eventually the Marine SSB channels transitioned to the present 3kHz spacing.

Mike N2MS
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