In days past, the telephone companies ran an analog carrier system of 24 SSB channels with what was called a pilot tone at a reduced level. The pilot was indeed a carrier reference that was PLL to the office master clock. These 0-4 Khz channels could get off on the receiving end, but a "satellite doppler" type tracking circuit PPL to the incoming pilot tone kept everything in the pass band of the specific crystal filters for each channel. Bear in mind we expected pilot error in the CPS range, rather than 10s or 100s of cycles.
I would think one can design this to work with today's digital components rather than use the "rock solid" crystal filters this L Multiplex phone equipment did back in the day. Connect the pilot tone receive PLL to control the receive RF oscillator. I suspect it would work if the barn door was not too wide for the PLL to lock on. May get expensive if you have to use the crystals from yesteryear.
73 Jim WA4IVM
On 1/10/2014 2:28 PM, Kevin Muenzler, WB5RUE wrote:
I doubt that it would be useful because the tolerances are extremely high in DTMF so if you are only a few Hz off the tones won't lock. FM might be ok but certainly not SSB. FM itself has its own problems on HF so that might not be useable either.
Kevin Muenzler, WB5RUE Grid-EL09uf Eagle Creek Observatory http://www.eaglecreekobservatory.org I'd be unstoppable if it weren't for law enforcement and physics
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Robert Bruninga Sent: Friday, January 10, 2014 11:10 AM To: aprssig@tapr.org Cc: amsat-bb@amsat.org Subject: [amsat-bb] DTMF on HF?
Has anyone had any experience with any success at DTMF working on HF for some rudimentary commands?
I know tuning is critical as well as inter-tone noise must be way down.
Just thought maybe someone has experimented with it.
Bob, WB4aPR _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb