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
Bob,
I don't have any experience using DTMF on HF but back in the day before satcom,
commercial marine HF SSB coast stations used a dual tone selective calling
system made by Lorain Electronics. The encoder used 11 tones, one each for the
digits 0-9 and a carrier tone. Each digit was
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
I sometimes listen to the HF ATC station from New York Center talking to the
planes going to the Caribbean while working on the laptop in the shack. They
transmit selcall to the planes to make sure they can be alerted. The selcall
code is always 4 letters. They send two tones I always thought
Since DTMF has two tones for each number, it would seem possible that
you could have some DSP detect the difference frequency of each pair and
then either adjust its decoders or QSY the receiver's VCO to get a lock.
There are a ton of small development boards like Raspberry PI that have
Unfortunately, in some cases the differences are very close. C and
3 have pairs with a differential only 1 Hz apart.
Perhaps some heuristic approach which examines several consecutive
tone-pairs, looking for a single offset that would make them all valid?
On 01/10/2014 06:31 PM, Joe Leikhim
The software could first solve for one pair of tones then another, then
add or subtract the offset and choose the pair that has the correct
fundamental tones.
--
Joe Leikhim
Leikhim and Associates
Communications Consultants
Oviedo, Florida
jleik...@leikhim.com
407-982-0446
, January 10, 2014 2:31 PM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] Re: DTMF on HF?
Since DTMF has two tones for each number, it would seem possible that you
could have some DSP detect the difference frequency of each pair and then
either adjust its decoders or QSY the receiver's VCO to get a lock
Message-
From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On
Behalf Of Howie DeFelice
Sent: Friday, January 10, 2014 12:18 PM
To: amsat-bb@amsat.org
Subject: [amsat-bb] Re: DTMF on HF?
Bob,
I don't have any experience using DTMF on HF but back in the day before
satcom
